> **Title**: The association between acquired rifamycin resistance and
> the pharmacokinetics of rifabutin and isoniazid among patients with
> HIV-related tuberculosis. v092004
>
> **Authors:** Marc Weiner MD^1^, Debra Benator MD^2^, William Burman
> MD^3^, Charles A. Peloquin PharmD^4^, Awal Khan PhD^5^, Andrew Vernon
> MD MHS^5^, Brenda Jones MD^6^, Claudia Silva-Trigo RN^6^, Zhen Zhao
> PhD^5^, Thomas Hodge PhD^5^ and the Tuberculosis Trials Consortium
>
> **Affiliations:** ^1^University of Texas Health Science Center San
> Antonio and South Texas Veterans Health Care System, San Antonio TX;
> ^2^VAMC and George Washington University Medical Center, Washington
> DC; ^3^Denver Public Health and Department of Medicine, University of
> Colorado Health Science Center, Denver CO, ^4^National Jewish Medical
> and Research Center and University of Colorado Schools of Pharmacy and
> Medicine, Denver, CO, ^5^Division of TB Elimination, Centers for
> Disease Control and Prevention, Atlanta GA, ^6^Los Angeles
> County/University of Southern California Medical Center, Los Angeles
> CA and the Tuberculosis Trials Consortium
>
> **Running Head:** Pharmacokinetics in HIV-related TB
>
> **Key words**: tuberculosis, HIV, rifabutin, isoniazid and
> pharmacokinetics
>
> **Contact Information:** Marc Weiner MD; VAMC; Division Infectious
> Diseases (111F); 7400 Merton Minter Blvd; San Antonio TX 78229-4404
>
> Telephone number- 210-617-5300 ext 6060 or 6381
>
> FAX number- 210-617-5297
>
> E-mail address- weiner@uthscsa.edu Word count (3065)
>
> **Abstract** (word count 239)
>
> **Background:** The occurrence of acquired rifamycin resistance
> despite use of directly observed therapy for tuberculosis treatment is
> associated with advanced HIV disease and highly intermittent drug
> administration. Beyond these associations, the pathogenesis of
> acquired rifamycin resistance is unknown. 
>
> **Methods:** We performed a pharmacokinetic substudy of patients in a
> treatment trial using twice-weekly rifabutin and isoniazid. 
>
> **Results:** Sixty percent (102) of 169 patients in the treatment
> trial participated in the pharmacokinetic substudy, including 7 of 8
> patients with acquired rifamycin resistant failure or relapse. Median
> rifabutin area under the concentration-time curve (AUC~0-24~) was
> lower in patients with acquired rifamycin resistance compared to
> patients without acquired rifamycin-resistant failure/relapse (median
> rifabutin AUC~0-24~ 3.3 vs. 5.2 μg\*hour/ml, P-Value = 0.06,
> Mann-Whitney Exact). In a multivariate logistic regression model with
> an adjustment for CD4 lymphocyte cell count (a factor associated
> acquired rifamycin resistance in the parent treatment study), lower
> rifabutin AUC~0-24~ was associated with acquired rifamycin resistance
> (Odds Ratio \[OR\] 7.6; 95% Confidence Intervals \[CI\], 1.3 -- 45.5,
> P-Value = 0.03). Median isoniazid AUC~0-12~ was not significantly
> associated with acquired rifamycin resistance (isoniazid AUC~0-12~
> 20.6 vs. 28.0 μg\*hour/ml, P-Value = 0.24, Mann-Whitney Exact), but
> there was an association in a multivariate logistic regression
> analysis adjusting for rifabutin AUC~0-24~ (isoniazid AUC~0-12~ OR
> 10.5; 95% CI, 1.1 -- 100, P-Value = 0.04).
>
> **Summary**: Lower plasma concentrations of rifabutin, and perhaps
> isoniazid, were related to the occurrence of treatment failure or
> relapse with acquired rifamycin resistance among patients with
> HIV-related tuberculosis treated with twice-weekly therapy.
>
> **Background**
>
> Directly observed therapy prevents selective drug-taking, and thereby
> generally prevents the acquisition of drug resistance during treatment
> of tuberculosis \[1\]. However, it has become increasingly clear that
> resistance to the rifamycin antibiotics (rifampin, rifabutin, and
> rifapentine) can be acquired despite use of directly observed therapy
> among patients with HIV infection \[2-4\]. The association was
> confirmed in Tuberculosis Trials Consortium (TBTC)/ United States
> Public Health Service (USPHS) Study 22 where 4 of 30 (13.3%)
> HIV-seropositive patients treated with once-weekly
> isoniazid/rifapentine developed acquired rifamycin resistant
> failure/relapse whereas no cases of acquired rifamycin resistance were
> identified among 502 HIV-negative patients treated with the same
> regimen \[5, 6\].  Among patients with HIV-related tuberculosis,
> consistent risk factors for acquired rifamycin resistance were
> reported to be low CD4 cell count and highly-intermittent (once or
> twice-weekly) tuberculosis therapy \[4-8\]. Apart from these
> associations, the pathogenesis of acquired rifamycin resistance
> remains speculative.
>
> TBTC/USPHS Study 23 was a study of HIV-infected patients with
> tuberculosis treated with a largely-intermittent (twice-weekly)
> rifabutin-containing regimen under direct supervision \[7\]. Although
> the overall rate of treatment failure or relapse in the study was
> similar to prior studies (9 \[5.3%\] of 169), enrollment into the
> trial was stopped because 8 of the 9 cases of treatment failure or
> relapse had acquired rifamycin resistance. To better understand the
> pathogenesis of acquired rifamycin resistance, we evaluated
> pharmacokinetic parameters of isoniazid and rifabutin among patients
> enrolled in the TBTC Study 23. Preliminary data were reported in the
> form of abstracts \[9, 10\].
>
> **Methods**
>
> **Experimental Design**
>
> Patients were enrolled non-randomly into the pharmacokinetic substudy
> in two phases (Figure 1). In the prospective phase, 98 (58%) of the
> 169 patients with HIV-associated tuberculosis were enrolled into the
> pharmacokinetic study during the two-drug phase of treatment
> (generally months 3-6 of therapy). The rifabutin dose was 300 mg, with
> adjustment for antiretroviral therapy following national guidelines
> when used with protease inhibitors or efavirenz \[11\]; the isoniazid
> dose was 15 mg/kg, to a maximum dose of 900 mg. Of the 98, one failed
> treatment (had a positive sputum culture between four months and the
> end of therapy) and two relapsed after study treatment. Four other
> patients underwent pharmacokinetic sampling after they had developed a
> treatment endpoint (retrospectively sampled patients): three with
> relapse after completion of study therapy, and one after treatment
> failure. The seven cases with acquired rifamycin resistant
> failure/relapse were followed from the start of induction-phase
> tuberculosis therapy for a median 254 (IQR 223-342) days. Of the 91
> patients without tuberculosis failure/relapse, ten died after
> follow-up for a median 594 (IQR 448-744) days, and 81 other patients
> were followed a median 918 (IQR 813-938) days. The pharmacokinetic
> substudy was approved by the Institutional Review Boards of the
> Centers for Disease Control and Prevention and the 26 participating
> TBTC sites.
>
> **Sample collection, drug and genotype analyses**
>
> Blood samples for analyses were collected just before an observed dose
> and then 1, 2, 3, 6 and 24 hours afterwards. Patients took medications
> under the same conditions (fasting or fed) that they received their
> TBTC Study 23 therapy. Standard techniques were used for plasma drug
> concentrations with validated HPLC analyses of isoniazid \[12\],
> rifabutin and 25-deacetyl metabolite and for N-acetyl-transferase
> genotyping \[13\].
>
> **Statistical and pharmacokinetic analyses**
>
> Patients sampled both prospectively during study therapy and
> retrospectively after completion of treatment were combined for the
> primary analyses, in order to compare all possible patients with
> failure/relapse to others enrolled in the study. However, one patient
> sampled retrospectively (Table 3, G) after treatment failure was
> excluded from the isoniazid analysis because as part of a daily
> re-treatment regimen, isoniazid 300 mg was administered for
> pharmacokinetic sampling. Another subject (Table 3, E) studied
> retrospectively after relapse was excluded from the rifabutin analysis
> because a blood sample 24 hours after drug administration was not
> obtained. Finally the rifabutin pharmacokinetic parameters in two
> subjects (Table 3, D and F) \-- each studied retrospectively after
> relapse with one dose of rifabutin 300 mg \-- were adjusted for
> auto-induction by decreasing the estimated rifabutin area under the
> concentration-time curve (AUC~0-24~) by 37.5% and by decreasing the
> maximal concentration (Cmax) by 11.6% \[14\]. In additional analyses,
> the associations of outcome with rifabutin AUC~0-24~ were examined
> without adjustments for rifabutin autoinduction, and also with only
> patients sampled prospectively during study therapy. Because the
> metabolism of isoniazid does not undergo induction, isoniazid
> parameters were not adjusted \[12, 15\].
>
> Analyses of pharmacokinetic parameters were performed using
> non-compartmental techniques (WinNonlin PK software, Pharsight Version
> 4, CA). Rifabutin is known to have an extended terminal elimination
> phase. Because it was not possible to accurately calculate rifabutin
> half-life with the sparse sampling scheme used, the parameter was not
> included in this analysis
>
> Data analyses were performed using SAS software (Cary, NC) and
> StatXact (Cambridge, MA). For dichotomous data, differences between
> groups were determined using the Fisher's Exact test or Chi Square
> statistic. For non-normally distributed data, the Mann-Whitney (Table
> 1 and 4) or Mann-Whitney Exact (Table 2) were used. Data were natural
> log-transformed (LN) if a normal distribution was rejected by the
> Shapiro-Wilk, or if variances of different groups were unequal and LN
> transformation improved the validity of the analyses (Table 5 and the
> multivariate regressions). LN transformed results were back
> transformed to the original scale to obtain mean and 95 percent
> confidence intervals. Differences between groups were considered
> statistically significant at a P-Value \< 0.05. We performed
> univariate analysis of epidemiologic, clinical and treatment factors
> in patients with acquired rifamycin resistance compared to other
> patients in the study. In multivariate logistic regression model,
> covariates found to be associated with increased risk of treatment
> failure or relapse were entered in a step-wise procedure to include
> rifabutin AUC~0-24~ adjusted for autoinduction (continuous variable),
> days per week of therapy during induction treatment phase (2, 3 or 5
> days as continuous variable) and CD4 lymphocyte cell count at
> tuberculosis diagnosis (continuous variable).  An alternative
> multivariate logistic regression model was examined with independent
> covariates with a probability \< 0.20 by univariate analysis. Odds
> ratios were expressed with LN transformed AUC (expressed as
> μg\*hour/ml) and CD4 cell count (cells/cc^3^).
>
> Finally, we analyzed factors associated with rifabutin AUC~0-24~ among
> all patients sampled. By ANCOVA in Table 5, rifabutin AUC~0-24~ was LN
> transformed and evaluated for demographic, clinical, and laboratory
> factors adjusted for drug dose. The group means of the LN rifabutin
> AUC~0-24~ and the 95% confidence interval of means were then
> transformed back to original units.

**Results**

> **Subjects**
>
> The demographics and clinical characteristics of the 102 patients in
> the pharmacokinetic substudy were similar in most respects to the
> other HIV-seropositive patients in Study 23 who did not participate
> (Table 1). However the CD4 cells counts were higher and cavitation was
> more common among patients who underwent pharmacokinetic sampling,
> suggesting that this population had somewhat less advanced HIV
> disease; fewer non-Hispanic Whites participated in the present study.
>
> **Association of rifabutin AUC~0-24~ with treatment outcome**
>
> Patients with acquired rifamycin resistant failure or relapse had
> lower rifabutin AUC~0-24~ compared to other patients without acquired
> rifamycin-resistant failure/relapse (rifabutin AUC~0-24~ 3.3 vs. 5.2
> μg\*hour/ml, P = 0.06, Mann-Whitney Exact) (Figure 2A, Table 2). This
> association was also seen in an analysis restricted to the 96 patients
> sampled prospectively during the treatment trial (rifabutin AUC~0-24~
> 2.0 vs. 5.2 μg\*hour/ml, P = 0.01, Mann-Whitney Exact). Finally in a
> multivariate logistic regression model adjusted for the clinical
> factor(s) associated with treatment failure or relapse in the parent
> treatment study (CD4 cell count at time of diagnosis of tuberculosis),
> rifabutin AUC~0-24~ was also significantly associated with
> failure/relapse (OR 7.6; 95% CI, 1.3 - 45.5, P-Value = 0.03).
> Alternative logistic regression models using multiple independent
> covariates (Table 4) yielded similar results. There was no association
> between AUC~0-24~ to the desacetyl rifabutin metabolite and acquired
> rifamycin resistance (Table 2).
>
> In an analyses of patients prospectively sampled, the median peak
> concentration of rifabutin was significantly lower with acquired
> rifamycin resistance compared to the other patients without acquired
> rifamycin-resistant failure/relapse (0.15 versus 0.45 μg/ml, P-Value =
> 0.03, Mann-Whitney Exact), although a significant difference in
> medians was not detected in all patients (0.30 versus 0.45 μg/ml,
> P-Value = 0.14, Mann-Whitney Exact).

**Isoniazid AUC~0-12~ and treatment outcome**

> Patients with acquired rifamycin resistance had somewhat lower
> isoniazid AUC~0-12~ than other patients without tuberculosis
> failure/relapse (isoniazid AUC~0-12~ 20.6 versus 28.0 μg\*hour/ml, P =
> 0.24, Mann-Whitney Exact) (Table 2, Figure 2B). The power of this
> comparison was limited by the small number of cases (N = 6) that could
> be included in the analysis. Furthermore, it is notable that Patient
> G, who could not be included in the analysis because of the isoniazid
> dose used (300 mg), had barely detectable isoniazid concentrations.
> Isoniazid acetylator status determined by N-acetyl-transferase type 2
> genotype was not associated with acquired rifamycin failure/relapse
> compared to other patients without acquired rifamycin-resistant
> failure/relapse (N = 74, P = 0.14, Chi Square). However in a logistic
> regression model with adjustment for rifabutin AUC~0-24~, isoniazid
> AUC~0-12~ was significantly associated with acquired rifamycin
> resistance (isoniazid LN AUC~0-12~ OR 10.5; 95% CI, 1.1 -- 100,
> P-Value = 0.04 with 5 events). As seen in Figure 3, all patients with
> acquired rifamycin resistance had low area under the
> concentration-time curve to rifabutin, isoniazid or both.
>
> **Factors associated with rifabutin AUC**
>
> By ANCOVA with demographic, clinical and treatment factors adjusted
> for dose, mean rifabutin AUC~0-24~ was significantly higher in
> patients who were younger or were receiving protease inhibitor-based
> antiretroviral therapy (Table 5). In multivariate ANCOVA, dose, age
> and protease inhibitor-based antiretroviral therapy were associated
> with rifabutin area under the concentration-time curve.
>
> **Discussion**
>
> This study suggests that the pharmacokinetics of rifabutin and
> isoniazid are important in the pathogenesis of acquired rifamycin
> resistance in HIV-related tuberculosis.  A clear association was found
> between decreased rifabutin AUC~0-24~ and acquired rifamycin
> resistance, despite the small number of cases with acquired rifamycin
> resistance available for analysis.  This association was retained in
> an analysis limited to prospectively-sampled patients and
> in multivariate analysis adjusting for CD4 cell count, a previously
> identified risk factor for acquired rifamycin resistance.  It is
> notable that our analysis probably overestimated rifabutin area under
> the concentration-time curve in patients with acquired rifamycin
> resistance (see issues summarized in Table 3).
>
> In this pharmacokinetic study, isoniazid AUC~0-12~ was lower in
> patients with acquired rifamycin resistant failure or relapse compared
> to others (median isoniazid AUC~0-12~ 20.6 vs. 28.0 μg\*hour/ml, P =
> 0.24), but the median difference was not statistically significant in
> univariate analysis.  However in a multivariate logistic regression
> model adjusting for rifabutin concentrations, isoniazid AUC~0-12~ was
> associated with acquired rifamycin resistant failure/relapse.
> Furthermore, additional comparisons suggested that low isoniazid area
> under the concentration-time curve may be important in the
> pathogenesis of acquired rifamycin resistance. Isoniazid AUC~0-12~ in
> patients enrolled prospectively in the present study were
> significantly lower than those of HIV-negative patients sampled in
> other TBTC studies (median isoniazid AUC~0-12~ 28 (IQR 17-45) vs. 49
> (32-67) μg\*hour/ml, P \< 0.0001, Mann-Whitney) \[16\]. The isoniazid
> pharmacokinetic data are consistent with prior findings in a murine
> model of tuberculosis where bactericidal activity was highly
> correlated with isoniazid area under the concentration-time curve/MIC
> \[17\].
>
> The association between acquired rifamycin resistance and low
> isoniazid concentrations was expected. Resistance is thought to
> emerge during periods of functional monotherapy during which strains
> resistant to the drug still present \-- in this case rifabutin \--
> would be selected.  That this occurs almost exclusively among patients
> with severe immunodeficiency (CD4 cell counts \< 75 in almost all
> cases) suggests that ineffective cellular immune function and marginal
> drug concentrations permit greater mycobacterial growth between doses
> of tuberculosis chemotherapy, and increased opportunity for rifamycin
> tolerance and/or selection of genomic resistance.
>
> However, the important finding in this study was the association
> between low rifabutin concentrations and acquired rifamycin
> resistance.  Mitchison \[18\] has suggested that (i) rifamycins have
> unique sterilizing activity against slowly- or
> intermittently-metabolizing bacilli that remain after the initial
> phase of multidrug therapy, and that (ii) low concentrations of
> rifamycins lead to inadequate mycobacterial suppression. Lower
> concentrations of rifabutin and isoniazid identified in our study are
> consistent with and extend the hypothesis. Notably, the associations
> of rifabutin pharmacokinetic-pharmacodynamic parameters with treatment
> outcome in the present study (Table 2) are similar to rifampin
> pharmacokinetic-pharmacodynamic parameters reported in a murine model
> of tuberculosis where rifampin AUC/MIC was better correlated with
> bactericidal activity compared to rifampin peak concentration or to
> time of rifampin concentration above MIC \[19\].
>
> Another factor postulated to be important in the pathogenesis of
> acquired rifamycin resistance is the disparity in half-lives of
> isoniazid and the long-acting rifamycins, rifabutin and rifapentine
> \[5, 20\].  The pharmacokinetic mismatch between rifapentine and
> isoniazid was thought to be one of the reasons for the high rate of
> acquired rifamycin resistance when patients with advanced HIV
> infection were treated with once-weekly rifapentine plus isoniazid
> \[5\]. There is a similar pharmacokinetic difference between rifabutin
> and isoniazid (with plasma half-lives of 35 vs. 2-5 hours,
> respectively), so this mismatch might be thought to be important in
> the occurrence of acquired rifamycin resistance in this twice-weekly
> regimen. However, two observational cohort studies \[8, 21\] have
> shown similar rates of acquired rifamycin resistance among
> HIV-infected patients treated with intermittent rifampin and isoniazid
> compared to patients treated with rifabutin and isoniazid. Because the
> half-lives of rifampin and isoniazid are similar, these studies
> suggest that a mismatch of pharmacokinetics is not a requirement for
> the development of acquired rifamycin resistance. Malabsorbtion of
> isoniazid in the presence of characteristic rifampin pharmacokinetics
> however can result in acquired rifamycin resistance relapse \[15\].
>
> By multivariate ANCOVA in the present study, rifabutin AUC~0-24~ was
> directly associated with age, protease inhibitor-based antiretroviral
> therapy and rifabutin dose. The inter-patient observations were
> similar to intra-patient (N = 7) change in a longitudinal, cross-over
> study of twice-weekly rifabutin 300 mg with no antiretroviral therapy
> compared to rifabutin 150 mg with nelfinavir-based antiretroviral
> therapy; the interaction resulted in a 27% median increase in
> rifabutin AUC~0-24~ (4.35 vs. 5.53 mcg\*hr/ml, P-Value = 0.18 Wilcoxon
> Signed Rank Test) \[23\]. Similarly, the increase in rifabutin
> AUC~0-24~ (Table 5) among patients taking rifabutin 600 mg with
> efavirenz-based antiretroviral therapy was comparable to the
> intra-patient (N = 15) change observed between twice-weekly rifabutin
> 300 mg compared to twice-weekly rifabutin 600 mg and daily efavirenz
> (mean rifabutin AUC~0-24~ 5.38 vs. 5.76 mcg\*hr/ml, P-Value = 0.07,
> Paired T-test) \[24\].
>
> This pharmacokinetic substudy has several important limitations.
> Pharmacokinetics were obtained in only seven patients with acquired
> rifamycin resistant failure or relapse, resulting in decreased power
> and reliability of study observations. However the pharmacokinetic
> substudy in 102 patients, included 7 of the 8 patients with acquired
> rifamycin resistance in the parent trial, is the largest study to date
> of drug pharmacokinetics in HIV-associated tuberculosis, and the first
> of drug pharmacokinetics associated with acquired rifamycin
> resistance. Four patients had pharmacokinetic sampling performed after
> completing their initial course of treatment, and it was possible that
> pharmacokinetic parameters among these patients would have been
> different if they had sampling prospectively performed during study
> treatment. After adjustment for the auto-induction effects of
> rifabutin, pharmacokinetic parameters of patients sampled
> retrospectively were similar to those of all patients sampled
> prospectively in this study. Further, patients who were only
> prospectively evaluated during study treatment also demonstrated an
> association between decreased rifabutin AUC~0-24~ and acquired
> rifamycin resistance. Thus, it was unlikely that our use of
> retrospective sampling resulted in an analysis bias. Our sampling
> scheme (six time points per patient) was not sufficient to determine
> some pharmacokinetic parameters, like half-life, with accuracy.
> However, the robustness of our findings suggests that this sampling
> scheme was sufficient to detect relevant differences in
> pharmacokinetic parameters. In addition, CD4 cell counts and HIV PCR
> RNA were not obtained contemporaneous to pharmacokinetic sampling, so
> that correlations could not be established between HIV surrogate
> markers and drug pharmacokinetics. Residual confounding by measured or
> unmeasured variables was possible, but the association between
> acquired rifamycin resistance and low rifabutin AUC~0-24~ remained
> strong in an analysis adjusting for risk factors for failure or
> relapse identified in the parent study.
>
> In summary, our study offers strong evidence that an important factor
> in the pathogenesis of acquired rifamycin resistance is abnormal
> pharmacokinetics of the drugs used to treat tuberculosis. The
> association with acquired rifamycin resistance was strongest for low
> rifabutin AUC~0-24~, but also suggestive for low isoniazid AUC~0-12~.
> Translating these results into clinical practice will require
> additional clinical trials. One could consider therapeutic drug
> monitoring of rifabutin and isoniazid among patients with tuberculosis
> and advanced HIV disease \[24\]. However, the expense of obtaining
> drug concentration data from multiple time points is considerable, and
> our results do not lend themselves to simple criteria for interpreting
> and acting upon the results of the data obtained. Treatment
> intensification with increased dosing frequency \[25\], and/or greater
> dosage may ameliorate the risk of abnormally low plasma concentrations
> of antituberculosis drugs, but requires further study to determine
> optimally effective regimens. Current recommendations propose using
> daily therapy, at least for the first two months of treatment among
> patients with advanced HIV disease \[11\]. Finally, these results
> illustrate the usefulness of incorporating pharmacokinetic
> measurements into studies evaluating new tuberculosis treatment
> regimens.
>
> **Contributors**
>
> The participating clinical sites (principal investigators and study
> coordinators \[numbers of patients enrolled\]) were: *Los Angeles
> County/University of Southern California Medical Center* (Brenda Jones
> MD, Claudia Silva RN, Maria Brown MPH \[15\]), *University of Texas
> Health Science Center in San Antonio/ South Texas Veterans Health Care
> System,* (Marc Weiner MD, Melissa Engle CRT, CCRC, Victoria Rodriguez
> RN \[12\]), *Johns Hopkins University School of Medicine* (Richard
> Chaisson MD, Tim Sterling MD, Kristina Moore RN, Judith Hackman RN
> \[11\]), *Nashville VA Medical Center* (Douglas Kernodle MD, Anthony
> Chapdelaine MD, Guat-Siew McKee MD, Linda Reeves-Hammock RN \[11\]),
> *University of North Texas Health Science Center* (Stephen Weis DO,
> Barbara King RN, Norma Shaffer LVN \[9\]), *Houston VA Medical Center*
> (Christopher Lahart MD, Ruby Nickson RN, Terry Scott RN, Robert Awe MD
> \[9\]), *New Jersey Medical School National TB Center -University of
> Medicine & Dentistry of New Jersey* (Bonita T. Mangura MD, Marilyn
> Owens RN, Cora Leus RN \[8\]), *Bellevue Hospital Center, New York
> University* (Neil Schluger MD, William Rom MD, Rany Condos MD, Laurie
> Sandman RN, MPH \[6\]), *Harlem Hospital Center* (Wafaa El-Sadr MD,
> Frantz Medard MD, Mary Klein RN \[4\]), *Carolinas Medical Center*
> (James Horton MD, Ann Boye RN, Beth Quinn RN \[4\]), *Denver Health
> and Hospitals* (Randall Reves MD, William Burman MD, Jan Tapy RN
> \[3\]), *San Francisco VA Medical Center* (Charles Daley MD, Llewellyn
> Stanton RN \[3\]), *University of Manitoba* (Earl Hershfield MD, Gerry
> Izon RN \[2\]), *Duke University Medical Center and Durham VA Medical
> Center* (Carol Dukes Hamilton MD, Ann Mosher RN \[2\]), *Veterans
> Affairs Medical Center-Washington DC* (Fred Gordin MD, Debra Benator
> MD, Donna Sepulveda Conwell RN, Thomas Walsh MD, Margaret Lankford RN,
> Charlotte Quinlan-Mauzy RN \[1\]), University of British Columbia
> Health Center (Mark Fitzgerald MB, Eduardo Hernandez MD, Banafsheh
> Peyvandi MD \[1\]), and Hines VA Medical Center and Suburban Cook
> County TB District, Illinois (Constance Pachuki MD, Mary Samuel RN,
> James Gallai MD \[1\]).
>
> [**Acknowledgements**](http://gateway1.ovid.com/ovidweb.cgi#29%2329)
>
> We are grateful to Drs. Rick O'Brien, Elsa Villarino and Kenneth
> Castro for their support and leadership within the CDC, to Ms. Lorna
> Bozeman for assistance with study logistics, and to Dr. C. Robert
> Horsburgh for review of the manuscript. The study was supported by the
> Centers for Disease Control and Prevention, United States Public
> Health Service. The manufacturer (Pharmacia-Adria) allowed the
> investigators access to their safety data regarding rifabutin. The
> Frederic C. Bartter General Clinical Research Center at the VAMC San
> Antonio supported by NIH Grant MO1-RR-01346 provided assistance in
> evaluation of some patients. All authors reported no conflict of
> interests.
>
> .
>
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> **2003**; 167: 603-62
>
> 12- Peloquin CA, Namdar R, Dodge AA, Nix DE. Pharmacokinetics of
> isoniazid under fasting -conditions, with food and with antacids. Int
> J Tuberc Lung Dis **1999**; 3: 703.
>
> 13- Cascorbi I, Roots I. Pitfalls in N-acetyltransferase 2 genotyping.
> Pharmacogenetics **1999**;9: 123-7.
>
> 14- Li RC, Narang PK, Pogesi I, Strolin-Benedetti M. A model based
> assessment of redistribution dependent elimination and bioavailability
> of rifabutin. Biopharm Drug Dispos **1996**; 17: 223-36.
>
> 15- Weiner M, Burman W, Vernon A, Tuberculosis Trials Consortium et
> al. Low isoniazid concentration associated with outcome of
> tuberculosis treatment with once-weekly isoniazid and rifapentine. Am
> J Respir Crit Care Med **2003**; 167:1341-7.
>
> 16- Weiner M, Burman W, Khan A, Tuberculosis Trials Consortium et al.
> The effect of HIV serostatus on isoniazid pharmacokinetics among
> patients with active tuberculosis Am J Respir Crit Care Med **2004**;
> 169: A260.
>
> 17- Jayaram R, Shandil R, Gaonkar S et al. Isoniazid
> pharmacokinetics-pharmacodynamics in an aerosol infection model of
> tuberculosis. Antimicrob Agents Chemother **2004**; 48: 2951-7.
>
> 18- Mitchison DA*.* Role of isoniazid in once-weekly rifapentine
> treatment of pulmonary tuberculosis. Am J Respir Crit Care Med
> **2003**; 167: 1298-9.
>
> 19- Jayaram R, Gaonkar S, Kaur P et al.
> Pharmacokinetics-pharmacodynamics of rifampin in an aerosol infection
> model of tuberculosis. Antimicrob Agents Chemother **2003**; 47:
> 2118-24.
>
> 20- Weiner M, Bock N, Peloquin CA, Tuberculosis Trials Consortium et
> al. Rifapentine Pharmacokinetics with 600, 900 or 1,200 mg Doses in
> Patients with Tuberculosis during Once-Weekly Continuation-Phase
> Therapy. Am J Respir Crit Care Med **2004**; 169: 1191-7.
>
> 21- Li J, Munsiff SS,  Driver CR, Sackoff J. Outcome of HIV-infected
> tuberculosis patients treated with rifabutin or rifampin-based
> regimens, New York City, 1997-2000.  \[Late-Breaker session on
> Tuberculosis\]. In: Program and abstracts of the 34th International
> Union Against Tuberculosis and Lund Disease World Conference, Paris,
> France: **2003**.
>
> 22- Benator D, Weiner M, Burman W, Vernon A, Zhao Z, Khan K, Sandman
> L, Engle M, Silva C, Peloquin C, Hsyu P, Becker M. Intensive
> pharmacokinetics of the nelfinavir - rifabutin Interaction in patients
> with HIV related tuberculosis treated with a twice-weekly
> rifabutin-based regimen *Am J Respir Crit Care Med.* **2004**; 169.
> A96.
>
> 23- Weiner M, Peloquin C, Khan A, Vernon A, Engle M, Benator D,
> Fitzgerald M, Zhao Z, Burman B and the Tuberculosis Trials Consortium.
> Intermittent rifabutin and isoniazid with daily efavirenz in
> combination with two nucleosides for treatment of HIV infection and
> tuberculosis disease. **2004**; \[abstract 350\].
> [http://www.retroconference.org/2004/AbstractSearch/AbstractSearch.aspx]{.underline}.
>
> 24- Peloquin CA. Therapeutic drug monitoring in the treatment of
> tuberculosis. Drugs **2002**; 62: 2169-83.
>
> 25- Sonnenberg P, Murray J, Glynn JR, et al. HIV-1 and recurrence,
> relapse, and reinfection of tuberculosis after cure: a cohort study in
> South African mineworkers. Lancet **2001**; 358: 1687-93.
>
> Table 1.  Demographic and clinical characteristics of patients
> enrolled in TBTC Study 23 who participated in the pharmacokinetic
> substudy compared to others who did not participate.

+-------------------------------------+------------+-----------+-------+
| Characteristic                      | In PK      | Not in PK | P-Val |
|                                     | Study ^a^  | Study     | ue^b^ |
|                                     | (percent)  | (percent) |       |
+-------------------------------------+------------+-----------+-------+
| Number (N^a^)                       | 102        | 67        |       |
+-------------------------------------+------------+-----------+-------+
| Age (years), median (IQR^a^)        | 41 (35-46) | 39        | 0.25  |
|                                     |            | (33-45)   |       |
+-------------------------------------+------------+-----------+-------+
| Male / female, N (%)                | 79 (78)    | 53 (79)   | 1.00  |
+-------------------------------------+------------+-----------+-------+
| Race / ethnicity                    |            |           |       |
+-------------------------------------+------------+-----------+-------+
|    Black, N (%)                     | 57 (56)    | 29 (43)   | 0.12  |
+-------------------------------------+------------+-----------+-------+
|    White, Hispanic, N (%)           | 35 (35)    | 19 (28)   | 0.41  |
+-------------------------------------+------------+-----------+-------+
|    White, non-Hispanic, N (%)       | 7 (7)      | 12 (18)   | 0.04  |
+-------------------------------------+------------+-----------+-------+
| Born in Mexico, N (%)               | 22 (22)    | 10 (15)   | 0.32  |
+-------------------------------------+------------+-----------+-------+
| Homeless within past year, N (%)    | 30 (30)    | 15 (22)   | 0.29  |
+-------------------------------------+------------+-----------+-------+
| Injection drug use within the past  | 10 (10)    | 7 (10)    | 0.46  |
| year, N (%)                         |            |           |       |
+-------------------------------------+------------+-----------+-------+
| Alcohol abuse within the past year, | 38 (38)    | 19 (28)   | 0.23  |
| N (%)                               |            |           |       |
+-------------------------------------+------------+-----------+-------+
| Body mass index at TB diagnosis,    | 21.5       | 20.9      | 0.55  |
| median (IQR)                        | (          | (1        |       |
|                                     | 18.5-24.1) | 8.6-23.1) |       |
+-------------------------------------+------------+-----------+-------+
| Site of involvement                 |            |           |       |
+-------------------------------------+------------+-----------+-------+
|    Pulmonary, N (%)                 | 56 (55)    | 37 (55)   | 0.97  |
+-------------------------------------+------------+-----------+-------+
|    Extra-pulmonary and pulmonary, N | 37 (36)    | 17 (25)   | 0.14  |
| (%)                                 |            |           |       |
+-------------------------------------+------------+-----------+-------+
| Presence of cavitation on chest     | 18 (18)    | 3 (5)     | 0.01  |
| radiograph, N (%)                   |            |           |       |
+-------------------------------------+------------+-----------+-------+
| Bilateral lung involvement on chest | 20 (20)    | 3 (5)     | 0.02  |
| radiograph, N (%)                   |            |           |       |
+-------------------------------------+------------+-----------+-------+
| Median CD4 cell count at TB         | 101        | 55        | 0.01  |
| diagnosis, median (IQR)             | (51-245)   | (29-135)  |       |
+-------------------------------------+------------+-----------+-------+
| Median HIV RNA (log 10) at TB       | 5.3        | 5.3       | 0.89  |
| diagnosis, median (IQR)             | (4.7-5.7)  | (4.9-5.3) |       |
+-------------------------------------+------------+-----------+-------+
| Use of twice weekly treatment       | 48 (48)    | 27 (42)   | 0.52  |
| during first two months of          |            |           |       |
| tuberculosis therapy, N (%)         |            |           |       |
+-------------------------------------+------------+-----------+-------+
| ^a^ IQR (interquartile range); N    |            |           |       |
| (number), PK (Pharmacokinetic)      |            |           |       |
|                                     |            |           |       |
| ^b^ P-Values by Mann-Whitney for    |            |           |       |
| continuous and by Fisher's Exact or |            |           |       |
| Chi-Square for dichotomous          |            |           |       |
| variables                           |            |           |       |
+-------------------------------------+------------+-----------+-------+

> Table 2: Association of pharmacokinetic parameters with acquired
> rifamycin resistant failure/relapse of tuberculosis.

+---------------------+---+---------------+----+----------------+-----+
| Pharmacokinetic     | N | Patients with | N  | Patients       | P   |
| parameter           |   | acquired      |    |                | -Va |
|                     |   | rifamycin     |    | without        | lue |
|                     |   | resistance    |    | acquired       | ^a^ |
|                     |   |               |    | rifamycin      |     |
|                     |   | Median (IQR)  |    | resistance     |     |
|                     |   |               |    |                |     |
|                     |   |               |    | Median (IQR)   |     |
+---------------------+---+---------------+----+----------------+-----+
| [Isonia             |   |               |    |                |     |
| zid]{.underline}^b^ |   |               |    |                |     |
+---------------------+---+---------------+----+----------------+-----+
| AUC~0-12~           | 6 | 20.6          | 89 | 28.0           | 0   |
|                     |   | (11.4-23.6)   |    | (16.6-45.5)    | .24 |
| Cmax                | 6 |               | 91 |                |     |
|                     |   | 7.8 (2.5-8.6) |    | 7.5 (5.0-10.1) | 0   |
|                     |   |               |    |                | .59 |
+---------------------+---+---------------+----+----------------+-----+
| [Rifabutin          |   |               |    |                |     |
| (Prospective and    |   |               |    |                |     |
| retrospective cases |   |               |    |                |     |
| with adjustment for |   |               |    |                |     |
| in                  |   |               |    |                |     |
| duction]{.underline |   |               |    |                |     |
| }^c^[)]{.underline} |   |               |    |                |     |
+---------------------+---+---------------+----+----------------+-----+
| AUC~0-24~           | 6 | 3.28          | 94 | 5.22           | 0   |
|                     |   | (1.95-4.28)   |    | (3.97-7.39)    | .06 |
| Cmax                | 6 |               | 95 |                | 0   |
|                     |   | 0.30          |    | 0.45           | .14 |
|                     |   | (0.15-0.46)   |    | (0.29-0.58)    |     |
+---------------------+---+---------------+----+----------------+-----+
| [Rifabutin          |   |               |    |                |     |
| (Prospective and    |   |               |    |                |     |
| retrospective cases |   |               |    |                |     |
| without adjustment  |   |               |    |                |     |
| for                 |   |               |    |                |     |
| indu                |   |               |    |                |     |
| ction)]{.underline} |   |               |    |                |     |
+---------------------+---+---------------+----+----------------+-----+
| AUC~0-24~           | 6 | 4.11          | 94 | 5.22           | 0   |
|                     |   | (1.95-6.85)   |    | (3.97-7.39)    | .31 |
| Cmax                | 6 |               | 95 |                |     |
|                     |   | 0.32          |    | 0.45           | 0   |
|                     |   | (0.15-0.53)   |    | (0.29-0.58)    | .21 |
+---------------------+---+---------------+----+----------------+-----+
| [Rifabutin          |   |               |    |                |     |
| (Prospective cases  |   |               |    |                |     |
| only)]{.underline}  |   |               |    |                |     |
+---------------------+---+---------------+----+----------------+-----+
| AUC~0-24~           | 3 | 1.95          | 93 | 5.22           | 0   |
|                     |   | (1.52-3.35)   |    | (3.97-7.39)    | .01 |
| Cmax                | 3 |               | 94 |                |     |
|                     |   | 0.15          |    | 0.45           | 0   |
|                     |   | (0.09-0.31)   |    | (0.29-0.58)    | .03 |
+---------------------+---+---------------+----+----------------+-----+
| [Deacetyl rifabutin |   |               |    |                |     |
| (Prospective and    |   |               |    |                |     |
| retrospective cases |   |               |    |                |     |
| without adjustment  |   |               |    |                |     |
| for                 |   |               |    |                |     |
| indu                |   |               |    |                |     |
| ction)]{.underline} |   |               |    |                |     |
+---------------------+---+---------------+----+----------------+-----+
| AUC~0-24~           | 6 | 0.77          | 85 | 0.72           | 0   |
|                     |   | (0.47-1.13)   |    | (0.55-1.60)    | .69 |
| Cmax                | 6 |               | 94 |                |     |
|                     |   | 0.05          |    | 0.06           | 0   |
| [Deacetyl rifabutin | 3 | (0.03-0.09)   | 94 | (0.04-0.10)    | .64 |
| (Prospective cases  |   |               |    |                |     |
| only)]{.underline}  | 3 | 0.45          | 94 | 0.71           | 0   |
|                     |   | (0.17-0.52)   |    | (0.47-1.26)    | .08 |
| AUC~0-24~           |   |               |    |                |     |
|                     |   | 0.03          |    | 0.06           | 0   |
| Cmax                |   | (0.01-0.04)   |    | (0.04-0.10)    | .10 |
+---------------------+---+---------------+----+----------------+-----+

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

(^a^) P-Value by Mann-Whitney Exact Test

(^b^) Analysis of isoniazid pharmacokinetics included combination of
both prospectively (N = 94) and retrospectively (N = 3) patients sampled
for pharmacokinetics relative to Study 23 continuation-phase therapy.

(^c^) Rifabutin pharmacokinetic parameters were adjusted for
autoinduction (8) in two patients with acquired rifamycin resistance
sampled retrospectively after Study 23 continuation-phase therapy and
sampled after administration of a single dose of rifabutin.

Table 3: Patients in Study 23PK who relapsed with acquired rifamycin
resistant tuberculosis.

+---+-------+-----+-----+-----+---------------------------------------+
| P | PK    | Dos | AUC |     | Comments                              |
| a | sam   | ing |     |     |                                       |
| t | pling |     | (d  |     |                                       |
| i | (Out  |     | rug |     |                                       |
| e | come) |     | d   |     |                                       |
| n |       |     | ose |     |                                       |
| t |       |     | mg) |     |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
|   |       |     | [R  | [I  |                                       |
|   |       |     | ifa | son |                                       |
|   |       |     | but | iaz |                                       |
|   |       |     | in] | id] |                                       |
|   |       |     | {.u | {.u |                                       |
|   |       |     | nde | nde |                                       |
|   |       |     | rli | rli |                                       |
|   |       |     | ne} | ne} |                                       |
|   |       |     | ^a^ | ^a^ |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| A | P     | Tw  | 1   | 21  | Estimated rifabutin AUC was lower     |
|   | rospe | ice | .38 | .71 | after PK sampling when efavirenz      |
|   | ctive | wee |     |     | based HAART was started, but          |
|   |       | kly | \   | \   | concomitant rifabutin dose not        |
|   | (fai  |     | (30 | (90 | increased.                            |
|   | lure) |     | 0\) | 0\) |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| B | p     | Tw  | 3   | 23  |                                       |
|   | rospe | ice | .81 | .58 |                                       |
|   | ctive | wee |     |     |                                       |
|   |       | kly | \   | \   |                                       |
|   | (rel  |     | (30 | (90 |                                       |
|   | apse) |     | 0\) | 0\) |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| C | p     | Tw  | 1   | 6   |                                       |
|   | rospe | ice | .95 | .46 |                                       |
|   | ctive | wee |     |     |                                       |
|   |       | kly | \   | \   |                                       |
|   | (rel  |     | (30 | (90 |                                       |
|   | apse) |     | 0\) | 0\) |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| D | ret   | Sin | 4   | 19  |                                       |
|   | rospe | gle | .28 | .47 |                                       |
|   | ctive |     |     |     |                                       |
|   |       | d   | \   | \   |                                       |
|   | (rel  | ose | (30 | (90 |                                       |
|   | apse) |     | 0\) | 0\) |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| E | ret   | Sin | \-  | 61  | Plasma rifabutin concentrations very  |
|   | rospe | gle |     | .39 | low, but case not included in main    |
|   | ctive |     | \   |     | rifabutin analysis because a 24 hour  |
|   |       | d   | (30 | \   | specimen was not obtained and very    |
|   | (rel  | ose | 0\) | (90 | late rifabutin absorption could not   |
|   | apse) |     |     | 0\) | be ruled out.                         |
+---+-------+-----+-----+-----+---------------------------------------+
| F | ret   | Sin | 2   | 11  |                                       |
|   | rospe | gle | .75 | .43 |                                       |
|   | ctive |     | (3  |     |                                       |
|   |       | d   | 00) | \   |                                       |
|   | (rel  | ose |     | (90 |                                       |
|   | apse) |     |     | 0\) |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| G | ret   | Pre | 9   | \-  | PK performed while on concurrent      |
|   | rospe | ced | .67 |     | nelfinavir and nevarapine             |
|   | ctive | ing |     | \   | antiretroviral therapy. Rifabutin AUC |
|   |       | d   | \   | (30 | obtained prior to protease inhibitor  |
|   | (fai  | ays | (30 | 0\) | treatment was estimated to be lower   |
|   | lure) | pr  | 0\) |     | than at PK sampling. Also, isoniazid  |
|   |       | ior |     |     | concentrations were almost            |
|   |       | to  |     |     | undetectable, but isoniazid AUC not   |
|   |       | PK  |     |     | included in the isoniazid analysis    |
|   |       | =   |     |     | because PK performed after            |
|   |       |     |     |     | administration of non-standard        |
|   |       | 1,  |     |     | isoniazid study dose                  |
|   |       | 0,  |     |     |                                       |
|   |       | 0,  |     |     |                                       |
|   |       |     |     |     |                                       |
|   |       | 1,  |     |     |                                       |
|   |       | 1,  |     |     |                                       |
|   |       | PK  |     |     |                                       |
+---+-------+-----+-----+-----+---------------------------------------+
| ( |       |     |     |     |                                       |
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| d |       |     |     |     |                                       |
| d |       |     |     |     |                                       |
| o |       |     |     |     |                                       |
| s |       |     |     |     |                                       |
| e |       |     |     |     |                                       |
| 1 |       |     |     |     |                                       |
| 5 |       |     |     |     |                                       |
| m |       |     |     |     |                                       |
| g |       |     |     |     |                                       |
| / |       |     |     |     |                                       |
| k |       |     |     |     |                                       |
| g |       |     |     |     |                                       |
| t |       |     |     |     |                                       |
| o |       |     |     |     |                                       |
| 9 |       |     |     |     |                                       |
| 0 |       |     |     |     |                                       |
| 0 |       |     |     |     |                                       |
| m |       |     |     |     |                                       |
| g |       |     |     |     |                                       |
| m |       |     |     |     |                                       |
| a |       |     |     |     |                                       |
| x |       |     |     |     |                                       |
| i |       |     |     |     |                                       |
| m |       |     |     |     |                                       |
| u |       |     |     |     |                                       |
| m |       |     |     |     |                                       |
| ) |       |     |     |     |                                       |
| . |       |     |     |     |                                       |
+---+-------+-----+-----+-----+---------------------------------------+

Table 4. Univariate analysis of demographic, clinical and treatment
factors with outcome of acquired rifamycin resistance

+---------------------------------------+-----------+-----------+-----+
| Characteristic                        | Patients  | Patients  | P   |
|                                       | [with]{.u | [wi       | --  |
|                                       | nderline} | thout]{.u | Va  |
|                                       | acquired  | nderline} | lue |
|                                       |           |           | ^b^ |
|                                       | rifamycin | acquired  |     |
|                                       | r         | rifamycin |     |
|                                       | esistance | r         |     |
|                                       |           | esistance |     |
|                                       | (N = 7)   |           |     |
|                                       |           | (N = 95)  |     |
+---------------------------------------+-----------+-----------+-----+
| **Demographic factors**               |           |           |     |
+---------------------------------------+-----------+-----------+-----+
| Median age (IQR ^a^)                  | 39        | 41        | 0   |
|                                       | (37-42)   | (34-47)   | .65 |
+---------------------------------------+-----------+-----------+-----+
| Sex, Male, N (%)                      | 6 (86)    | 74 (78)   | 1   |
|                                       |           |           | .00 |
+---------------------------------------+-----------+-----------+-----+
| Race/ethnicity, vs. all others, N (%) |           |           |     |
+---------------------------------------+-----------+-----------+-----+
|    -Hispanic                          | 5 (71)    | 32 (34)   | 0   |
|                                       |           |           | .10 |
+---------------------------------------+-----------+-----------+-----+
|    -White, non-Hispanic               | 0 (0)     | 7 (100)   | 1   |
|                                       |           |           | .00 |
+---------------------------------------+-----------+-----------+-----+
|    -Black                             | 2 (29)    | 54 (57)   | 0   |
|                                       |           |           | .24 |
+---------------------------------------+-----------+-----------+-----+
| Born in Mexico, N (%)                 | 4 (57)    | 19 (20)   | 0   |
|                                       |           |           | .04 |
+---------------------------------------+-----------+-----------+-----+
| Median body-mass index at TB          | 19.9      | 21.5      | 0   |
| diagnosis (IQR)                       | (1        | (1        | .77 |
|                                       | 7.8-26.0) | 8.6-24.1) |     |
+---------------------------------------+-----------+-----------+-----+
| **Clinical factors**                  |           |           |     |
+---------------------------------------+-----------+-----------+-----+
| Site of TB involvement, N (%)         |           |           |     |
+---------------------------------------+-----------+-----------+-----+
| -Pulmonary only                       | 2 (29)    | 54 (57)   | 0   |
|                                       |           |           | .24 |
+---------------------------------------+-----------+-----------+-----+
| -Both pulmonary and extrapulmonary    | 3 (43)    | 34 (36)   | 0   |
|                                       |           |           | .70 |
+---------------------------------------+-----------+-----------+-----+
| Presence of cavitation on chest       | 1 (17)    | 19 (20)   | 1   |
| radiograph, N (%)                     |           |           | .00 |
+---------------------------------------+-----------+-----------+-----+
| Bilateral lung involvement on chest   | 1 (14)    | 17 (18)   | 1   |
| radiograph, N (%)                     |           |           | .00 |
+---------------------------------------+-----------+-----------+-----+
| Median CD4 cell count at TB diagnosis | 28        | 112       | 0.  |
| (IQR)                                 | (21-43)   | (55-259)  | 001 |
+---------------------------------------+-----------+-----------+-----+
| Median HIV RNA (log 10) at TB         | 5.4       | 5.3       | 0   |
| diagnosis (IQR)                       | (5.2-5.6) | (4.7-5.8) | .69 |
+---------------------------------------+-----------+-----------+-----+
| **Tuberculosis treatment**            |           |           |     |
+---------------------------------------+-----------+-----------+-----+
| Use of twice-weekly therapy during    | 5 (71)    | 44 (46)   | 0   |
| induction phase, N (%)                |           |           | .26 |
+---------------------------------------+-----------+-----------+-----+
|   Drug pharmacokinetics, Median (IQR) |           |           |     |
+---------------------------------------+-----------+-----------+-----+
|    -Isoniazid AUC~0-12~ (μg\*hour/ml) | 20.6      | 28.0      | 0   |
|                                       | (1        | (1        | .23 |
|                                       | 1.4-23.6) | 6.6-45.5) |     |
+---------------------------------------+-----------+-----------+-----+
|    -Rifabutin AUC~0-24~ (μg\*hour/ml) | 3.28      | 5.22      | 0   |
|                                       | (1        | (3        | .06 |
|                                       | .95-4.28) | .97-7.39) |     |
+---------------------------------------+-----------+-----------+-----+
| (^a^) IQR (interquartile range)       |           |           |     |
|                                       |           |           |     |
| (^b^) P-Values by Mann-Whitney for    |           |           |     |
| continuous and by Chi-Square or       |           |           |     |
| Fisher's Exact for dichotomous        |           |           |     |
| covariates                            |           |           |     |
+---------------------------------------+-----------+-----------+-----+

Table 5. Effects of demographic, clinical and treatment factors on
rifabutin area under the concentration-time curve.

+----------------------------------+-----------+-----+-----------+-----+
| Factor (N = 100)                 | Rifabutin | P   | Rifabutin | P   |
|                                  | AUC~0-24~ | -Va | AUC~0-24~ | -Va |
|                                  |           | lue |           | lue |
|                                  |           |     | adjusted  |     |
|                                  |           |     | for dose  |     |
+----------------------------------+-----------+-----+-----------+-----+
|                                  | Mean (95% |     | Mean (95% |     |
|                                  | CI)^a^    |     | CI)^b^    |     |
+----------------------------------+-----------+-----+-----------+-----+
| Rifabutin dose [\<]{.underline}  | 4.70      | 0.  |           |     |
| 300 mg (N = 80)                  | (4        | 008 |           |     |
|                                  | .21-5.25) |     |           |     |
+----------------------------------+-----------+-----+-----------+-----+
| rifabutin dose \> 300 mg (N =    | 6.69      |     |           |     |
| 20)                              | (5        |     |           |     |
|                                  | .05-8.88) |     |           |     |
+----------------------------------+-----------+-----+-----------+-----+
| Age \< Median, 40 yrs            | 5.68      | 0   | 5.74      | 0   |
|                                  | (4        | .03 | (4        | .01 |
|                                  | .99-6.47) |     | .98-6.61) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [\>]{.underline} Median, 40 yrs  | 4.48      |     | 4.44      |     |
|                                  | (3        |     | (3        |     |
|                                  | .79-5.30) |     | .85-5.11) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Sex, Male (N = 79)               | 5.00      | 0   | 4.98      | 0   |
|                                  | (4        | .77 | (4        | .62 |
|                                  | .45-5.62) |     | .43-5.59) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Female (N = 21)                  | 5.21      |     | 5.31      |     |
|                                  | (3        |     | (4        |     |
|                                  | .96-6.84) |     | .24-6.65) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [Race / ethnicity]{.underline}   |           |     |           |     |
+----------------------------------+-----------+-----+-----------+-----+
| Non-Hispanic White (N = 7)       | 5.56      | 0   | 5.62      | 0   |
|                                  | (3        | .63 | (3        | .58 |
|                                  | .81-8.11) |     | .80-8.30) |     |
+----------------------------------+-----------+-----+-----------+-----+
| vs. others                       | 5.01      |     | 5.00      |     |
|                                  | (4        |     | (4        |     |
|                                  | .48-5.61) |     | .50-5.57) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Hispanic White ( N = 56)         | 5.56      | 0   | 5.60      | 0   |
|                                  | (4        | .19 | (4        | .15 |
|                                  | .73-6.54) |     | .76-6.59) |     |
+----------------------------------+-----------+-----+-----------+-----+
| vs. others                       | 4.79      |     | 4.77      |     |
|                                  | (4        |     | (4        |     |
|                                  | .16-5.51) |     | .20-5.42) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Black (N = 56)                   | 4.70      | 0   | 4.66      | 0   |
|                                  | (4        | .13 | (4        | .09 |
|                                  | .01-5.50) |     | .06-5.34) |     |
+----------------------------------+-----------+-----+-----------+-----+
| vs. others                       | 5.53      |     | 5.59      |     |
|                                  | (4        |     | (4        |     |
|                                  | .83-6.33) |     | .79-6.51) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Weight \< Median, 65 kg          | 5.20      | 0   | 5.19      | 0   |
|                                  | (4        | .47 | (4        | .49 |
|                                  | .47-6.06) |     | .49-6.00) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [\>]{.underline} Median, 65 kg   | 4.81      |     | 4.82      |     |
|                                  | (4        |     | (4        |     |
|                                  | .12-5.61) |     | .17-5.58) |     |
+----------------------------------+-----------+-----+-----------+-----+
| BMI at PK \< Median, 22          | 5.32      | 0   | 5.39      | 0   |
|                                  | (4        | .24 | (4        | .15 |
|                                  | .60-6.14) |     | .65-6.24) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [\>]{.underline} Median, 22      | 4.68      |     | 4.63      |     |
|                                  | (3        |     | (4        |     |
|                                  | .98-5.50) |     | .01-5.34) |     |
+----------------------------------+-----------+-----+-----------+-----+
| Other AIDS-defining condition(s) | 5.87      | 0   | 5.70      | 0   |
| (N = 9)                          | (4        | .38 | (4        | .47 |
|                                  | .15-8.32) |     | .04-8.04) |     |
+----------------------------------+-----------+-----+-----------+-----+
| No other AIDS-defining           | 4.97      |     | 4.99      |     |
| condition(s) (N = 91)            | (4        |     | (4        |     |
|                                  | .44-5.57) |     | .47-5.55) |     |
+----------------------------------+-----------+-----+-----------+-----+
| HIV RNA viral load^c^ (\<        | 5.33      | 0   | 5.18      | 0   |
| Median, 32,000 copies) (N = 46)  | (4        | .34 | (4        | .65 |
|                                  | .58-6.20) |     | .50-5.97) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [\>]{.underline} Median, 32,000  | 4.81      |     | 4.94      |     |
| copies (N = 46)                  | (4        |     | (4        |     |
|                                  | .14-5.59) |     | .29-5.70) |     |
+----------------------------------+-----------+-----+-----------+-----+
| CD4 cell count^d^                | 5.18      | 0   | 5.22      | 0   |
| [\<]{.underline} 75 cells /      | (4        | .63 | (4        | .54 |
| mm^3^) (N = 32)                  | .20-6.39) |     | .35-6.28) |     |
+----------------------------------+-----------+-----+-----------+-----+
| \> 75 cells / mm^3^ (N = 61)     | 4.88      |     | 4.86      |     |
|                                  | (4        |     | (4        |     |
|                                  | .27-5.59) |     | .26-5.55) |     |
+----------------------------------+-----------+-----+-----------+-----+
| [Antiretroviral therapy (^e^)    |           |     |           |     |
| with PK sampling]{.underline}    |           |     |           |     |
+----------------------------------+-----------+-----+-----------+-----+
| PI-based ART (N = 22)            | 6.52      | 0.  | 6.79      | 0.0 |
|                                  | (5        | 004 | (5        | 009 |
|                                  | .37-7.92) |     | .47-8.42) |     |
+----------------------------------+-----------+-----+-----------+-----+
| vs. no or NRTI-only ART (N = 66) | 4.42      |     | 4.36      |     |
|                                  | (3        |     | (3        |     |
|                                  | .86-5.07) |     | .85-4.94) |     |
+----------------------------------+-----------+-----+-----------+-----+
| EFV-based ART (N = 7)            | 6.81      | 0   | 4.96      | 0   |
|                                  | (4        | .05 | (3        | .76 |
|                                  | .82-9.62) |     | .36-7.31) |     |
+----------------------------------+-----------+-----+-----------+-----+
| vs. no or NRTI-only ART (N = 66) | 4.42      |     | 4.58      |     |
|                                  | (3        |     | (3        |     |
|                                  | .86-5.07) |     | .99-5.26) |     |
+----------------------------------+-----------+-----+-----------+-----+
|                                  |           |     |           |     |
+----------------------------------+-----------+-----+-----------+-----+

+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
|                                      |          |           |       |
+--------------------------------------+----------+-----------+-------+
| ^\_\_\_\_\_\_\_\_\_\                 |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\ |          |           |       |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_^ |          |           |       |
|                                      |          |           |       |
| > (^a^) Factor means, 95% Confidence |          |           |       |
| > Intervals and P-Value by ANOVA.    |          |           |       |
| >                                    |          |           |       |
| > (^b^) Factor means, 95% Confidence |          |           |       |
| > Intervals and P-Value adjusted for |          |           |       |
| > rifabutin dose by ANCOVA.          |          |           |       |
| >                                    |          |           |       |
| > (^c^) HIV RNA viral load was       |          |           |       |
| > obtained at (or if unavailable,    |          |           |       |
| > prior to) enrollment into TBTC     |          |           |       |
| > Study 23, a median of 66 (IQR,     |          |           |       |
| > 31 - 100) days prior to            |          |           |       |
| > pharmacokinetic sampling.          |          |           |       |
| >                                    |          |           |       |
| > (^d^) CD4 lymphocyte cell count /  |          |           |       |
| > mm^3^ obtained at enrollment into  |          |           |       |
| > TBTC Study 23, a median of 49      |          |           |       |
| > (IQR, 27-89) days prior to         |          |           |       |
| > pharmacokinetic sampling.          |          |           |       |
| >                                    |          |           |       |
| > (^e^) PI, protease inhibitor; EFV, |          |           |       |
| > efavirenz; NEV, nevarapine; ART,   |          |           |       |
| > antiretroviral therapy             |          |           |       |
+--------------------------------------+----------+-----------+-------+

Figure Legend

Figure 1. Enrollment groups in the pharmacokinetic study.

Figure 2. Box plot of (2A) of rifabutin area under the
concentration-time curve (AUC~0-24~) in patients with cure (n=84,)
versus acquired rifamycin resistant relapse (n=6,), and (2B) isoniazid
area under the concentration-time curve (AUC~0-12~) in patients with
cure (n = 81, ) versus acquired rifamycin resistant relapse (n = 6,).
Two cases sampled for pharmacokinetics after a single dose of rifabutin
had the AUC~0-24~ adjusted for multiple doses \[14\]. The 25^th^ and
75^th^ percentile are indicated by the bottom and top of the boxes, and
the 10^th^ and 90^th^ percentiles by brackets, the 95 percent confidence
intervals for the median by notches, and outlying cases by open circles
().

Figure 3. Bivariate scattergram of area under the concentration time
curves of rifabutin (Y-axis, rifabutin AUC~0-24~ μg\*h/ml) compared to
isoniazid (X-axis, INH AUC~0-12~ μg\*h/ml). Indicated in the plot are
patients with acquired rifamycin resistant treatment failure/relapse (N
= 5, ), or the other patients who did not fail or relapse with
rifamycin-resistant tuberculosis (N = 90, ). Cases 'E' and 'G' (Table
3) with acquired rifamycin resistant treatment failure/relapse had low
drug AUCs for rifabutin or isoniazid, respectively, and are indicated by
'block arrows'.

Figure 1. Enrollment groups in the pharmacokinetic study.

Figure 2A.

![](media/image1.wmf){width="4.995833333333334in"
height="3.751388888888889in"}

Figure 2B.

![](media/image2.wmf){width="4.995833333333334in"
height="3.751388888888889in"}

Figure 3.

> ![](media/image2.wmf)