bluuebunny/crossref_metadata_2025 huggingface dataset:
Clearance of Fentanyl, Alfentanil, Methohexitone, Thiopentone and Ketamine in Relation to Estimated Hepatic Blood Flow in Several Animal Species: Application to Prediction of Clearance in Man
Authors: Björkman Sven , Redke Finn
Published: July 2003

We have used estimated hepatic blood flow (Qhep) as an aid to evaluate clearance (CL) values in animals and to predict clearance in man of five anaesthetic agents: fentanyl, alfentanil, methohexitone, thiopentone and ketamine.

The disposition of methohexitone was determined in rats and that of ketamine in rats, rabbits and pigs. Further data were compiled from the literature and supplemented experimentally as needed. Allometric interspecies scaling, according to three different methods, was used to estimate blood clearance and unbound clearance (CLu) in man. The results of scaling according to the three different methods were evaluated in relation to estimated hepatic extraction ratio (CL/Qhep) of the drugs.

In most animals the clearance of the drugs were comparable with or lower than estimated Qhep. However, ketamine showed extensive extrahepatic clearance in rabbits. Prediction of clearance in man was successful by at least one method for all five drugs, while prediction of CLu generally failed. Estimates of CL/Qhep gave no indication as to the choice of the best method. Volume of distribution at steady state could be predicted for alfentanil, thiopentone and ketamine.

Comparison of clearance with Qhep should be used to evaluate clearance data in animals, however estimation of hepatic extraction ratios appears to be of little use for allometric scaling. The use of ketamine as an anaesthetic agent in rabbits is questionable, while the use of fentanyl in pigs, methohexitone in rats and ketamine in rats and pigs is well supported by the pharmacokinetic data.
Comparative Pharmacodynamics and Pharmacokinetics of Candesartan and Losartan in Man
Authors: Fuchs Bettina , Breithaupt-Grögler Kerstin , Belz Gustav G , Roll Susanna , Malerczyk Claudius , Herrmann Volker , Spahn-Langguth Hildegard , Mutschler Ernst
Published: July 2003

The angiotensin II antagonistic effects of candesartan and losartan were compared in-vivo after single and repeated doses. Effects were related to antagonistic activity in plasma.

In this double-blind, crossover study, 12 healthy male volunteers received, in random order, daily oral doses of 8 mg candesartan cilexetil or 50 mg losartan for seven days. On day 1 and day 8, dynamics and kinetics were assessed up to 48 h after dosing. Antagonistic effect was determined from the antagonist-induced rightward shifts of the diastolic blood pressure response curves to exogenously administered angiotensin II measured as the dose ratio (DR). The antagonistic activity in plasma was measured using an ex-vivo/in-vitro radioreceptor assay. Specific high-performance liquid chromatography assays determined plasma concentrations of candesartan, losartan and its active metabolite EXP-3174.

The pharmacokinetic properties of candesartan and losartan were comparable and antagonistic activity in plasma almost identical (ratio candesartan: losartan = 0.97 and 1.2 after single and multiple doses, respectively). However, the antagonistic effects of candesartan and losartan in-vivo were quite different. Twenty-four hours after single dosing with candesartan a clinically relevant rightward shift in the angiotensin II dose-response curve (DR = 3.2) occurred that was more pronounced than that following losartan administration (DR = 2.1, ratio candesartan: losartan = 1.65). Twenty-four hours after multiple doses of candesartan or losartan, the values of the DR were 4.8 and 2.3, respectively (ratio candesartan: losartan = 1.94). The values of DR for candesartan were significantly higher compared with losartan between 6 and 36 h after a single dose and between 3 and 24 h post-dose following multiple dose administration. A counter-clockwise hysteresis was apparent between antagonistic activity in plasma and antagonistic effect.

Despite equivalent angiotensin II antagonistic activity in plasma, the pharmacodynamic effect of candesartan cilexetil was greater than that of losartan. Candesartan appeared to have a slower off-rate from the angiotensin AT1-receptor compared with losartan, nevertheless differences in distributional phenomena or the extent of insurmountable antagonistic activity cannot be ruled out.
Chronopharmacokinetics of Sumatriptan in Healthy Human Subjects
Authors: Poondru Srinivasu , Devaraj Rambhau , Boinpally Ramesh R , Yamasani Madhusudan R
Published: July 2003

Rhythms in the onset and symptoms of several diseases are well established. Migraine is a disorder that exhibits periodicity in its symptoms and so chronotherapy may be beneficial in treating the problem. Designing a chronotherapeutic schedule requires chronopharmacokinetic and chronopharmacodynamic data of the drugs prescribed. We have studied the chronopharmacokinetics of sumatriptan, a drug of choice in migraine treatment.

Twelve healthy male volunteers were treated with 100 mg sumatriptan orally at 0700, 13 00, 19 00 and 01 00 h in a randomized 4 times 4 Latin square crossover design, with a washout period of one week. Serum samples were analysed by high performance liquid chromatography with an electrochemical detector. Pharmacokinetic parameters were calculated using noncompartmental methods. The pharmacokinetic parameters were analysed using analysis of variance and a two-tailed paired t-test at the probability of 95%.

The mean peak serum concentration following the 07 00 h administration (Cmax; 59.09 ± 10.53 ng mL−1) was significantly (P < 0.05; n = 12) higher than after the 19 00 h administration (Cmax 41.88 ± 12.21 ng mL−1). The mean area under the serum concentration-time curve from time zero to the last time-point (AUC0-t), the area under the serum concentration-time curve from zero to infinity (AUC0-∞), and the area under the first moment curve (AUMC) were significantly (P < 0.05; n = 12) higher following the 07 00 and 01 00 h administrations than after the 19 00 h administration. Following administration at 07 00 h, the mean oral clearance (CLs/f; 781 ± 186 mL h−1 kg−1) and the apparent volume of distribution (Vd/f; 2379 ± 684) were significantly lower (P < 0.05; n = 12) than after the 19 00 h administration (CLs/f 1208 ± 458 mL h−1 kg−1, Vd/f 4655 ± 2096 mL kg−1). The mean Vd/f value was again lower after the 1300h administration than after the 19 00 h administration (2763 ± 1417 vs 4655 ± 2096 mL kg−1; P < 0.05; n = 12).

The variations may be due to the time dependent changes in the extent of absorption and/or circadian variations in hepatic blood flow.
The Kinetic Profile of Gentamicin in Premature Neonates
Authors: Rocha M J , Almeida A M , Afonso E , Martins V , Santos J , Leitão F , Falcão A C
Published: July 2003

The kinetic profile of gentamicin in premature infants has been studied to enable the development of optimized dosage schedules for neonatal intensive-care units and to stress the relationship between the pharmacokinetic parameters and several demographic, developmental and clinical factors which might be associated with changes in gentamicin disposition.

Sixty-eight newborn patients of 24- to 34-weeks gestational age and 600–3100 g current weight in their first week of life, undergoing routine therapeutic drug monitoring of their gentamicin serum levels, were included in this retrospective analysis.

Gentamicin pharmacokinetic parameters were determined through non-linear regression by using a single-compartment open model. By regression analysis the current weight (g) was shown to be the strongest co-variate, and both gentamicin clearance (Lh−1) and volume of distribution (L) had to be normalized. Additionally, gentamicin clearance depended on gestational age with a cut-off at 30 weeks, which allowed the division of the overall population into two subsets (< 30 weeks and between 30–34 weeks of gestational age).

The younger neonates (< 30 weeks of gestational age) showed a lower gentamicin clearance (0.0288 vs 0.0340 Lh−1 kg−1), a slightly higher volume of distribution (0.464 vs 0.435 L kg−1), and a longer half-life (11.17 vs 8.88 h) compared with the older subgroup (30.34 weeks of gestational age).

On the basis of the pharmacokinetic parameters obtained, we suggest loading doses of 3.7 and 3.5 mg kg−1 for the two subgroups of neonates (<30 weeks and 30–34 weeks of gestational age), respectively. The appropriate maintenance doses in accordance with the characteristics of the patients should be 2.8 mg kg−1/24h and 2.6 mg kg−1/18h for neonates < 30 weeks and between 30–34 weeks of gestational age, respectively. Finally, when compared with previous studies, the information obtained on the pharmacokinetics and determinants of the pharmacokinetic variability of gentamicin in neonates was shown to be consistent.
Pharmacokinetics and Hepatoprotective Effects of 2-Methylaminoethyl-4,4‘-diiiethoxy-5,6,5’,6‘-dimethylenedioxybiphenyl-2-carboxylic acid-2’-carboxylate monohydrochloride in Rats with CCl4-induced Acute Hepatic Failure
Authors: Oh S Y , Lee C H , Ku Y S
Published: July 2003

The pharmacokinetics and hepatoprotective effects of 2-methylaminoethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylenedioxybiphenyl-2-carboxylic acid-2′-carboxylate monohydrochloride (DDB-S) have been investigated in rats with CCl4-induced acute hepatic failure.

To study the pharmacokinetics of DDB-S, rats were divided into a control group and a CCl4-intoxicated group. DDB-S 50 mg kg−1 was administered by intravenous bolus injection to both groups of rats. In the CCl4-intoxicated rats the plasma concentrations of DDB-S were significantly higher, the area under the plasma concentration-time curve from time zero to time infinity was significantly greater (6.46 vs 3.34 mg min mL−1), and the total body (7.74 vs 15.0 mL min−1 kg−1), renal (2.55 vs 5.10 mL min−1 kg−1), nonrenal (5.07 vs 9.65 mL min−1 kg−1), and biliary (1.48 vs 2.69 mL min−1 kg−1) clearances were significantly slower compared with the control rats. This could be due to decreased hepatic cytochrome P450 activity and impaired kidney function induced by CCl4.

To study the hepatoprotective effects of DDB-S, rats were divided into three groups, control rats and CCl4-intoxicated rats with or without DDB-S pretreatment (50 mg kg−1, i.p.). The effects of DDB-S pretreatment on CCl4-induced liver injury were considerable; the serum levels of alanine transaminase, aspartate transaminase, and alkaline phosphatase were significantly lower by 54.3, 44.6 and 67.2%, respectively, compared with the CCl4-intoxicated-only group.

In an in-vitro study, rat hepatocytes were exposed to fresh medium containing 10 mM CCl4 and various concentrations of DDB-S (10 or 100 μg mL−1). The levels of alanine transaminase and aspartate transaminase in the medium were measured as an indicator of hepatocyte injury. DDB-S dose-dependently decreased the levels of alanine transaminase and aspartate transaminase compared with CCl4-intoxication only.

These results indicate that DDB-S has hepatoprotective activity.
Analogues of Arginine Vasopressin Modified in Position 2 or 3 with Naphthylalanine: Selective Antagonists of Oxytocin In-vitro
Authors: Sobocińska M , Lempicka E , Konieczna E , Derdowska I , Lammek B , Melhem S , Kozik W , Janecka J , Janecki M , Trzeciak H I
Published: July 2003

In this study we describe the synthesis and some pharmacological properties of six new analogues of arginine vasopressin (AVP).

Five of the peptides were substituted in position 2 with L-1-naphthylalanine (L-1-Nal) or D-1-naphthylalanine (D-1-Nal); one had D-1-Nal in position 3. All analogues were tested in bioassays for pressor and antidiuretic activity. We also tested the uterotonic activity of the peptides in-vitro. Two of the new peptides were moderately potent V1a and oxytocin antagonists. The modifications proposed resulted in a drop or the removal of antidiuretic activity and in the removal of pressor activity, or conversion into moderate antagonists. Two peptides ([Mpa1, (L-1-Nal)2]AVP and [Mpa1, (D-1-Nal)2]AVP) which appear not to interact with V1a and V2 receptors were exceptionally selective oxytocin antagonists in-vitro.

These compounds with selective oxytocin antagonistic activity may be promising candidates for the development of potential tocolytic agents for the prevention of pre-term labour.
Development of Anti-influenza Drugs: II. Improvement of Oral and Intranasal Absorption and the Anti-influenza Activity of Stachyflin Derivatives
Authors: Yoshimoto J , Yagi S , Ono J , Sugita K , Hattori N , Fujioka T , Fujiwara T , Sugimoto H , Hashimoto N
Published: July 2003

The in-vivo anti-influenza-virus activity of Stachyflin derivatives (III and its phosphate ester, III-Phos), a new class of haemagglutinin fusion inhibitor, and the improvement of their absorption after oral or intranasal administration were studied in mice, rats, and ferrets.

The absorption of III in PEG 4000 and III-Phos aqueous solution increased about three and four fold in AUC after oral administration to uninfected mice compared with that of 0.5% HPMC (hydroxypropyl-methylcellulose) suspension. Using a mouse influenza virus infection model, significant anti-influenza-virus activity was observed in infected mice treated orally with these compounds dissolved in PEG 4000 or distilled water, respectively, but not in mice treated with 0.5% HPMC. The in-vivo anti-influenza-virus activity in ferrets, a good model for influenza virus infection in man, was also studied. Although the concentration of III in plasma was above the IC50 against the influenza virus strain used for 6h after the oral administration of III in PEG 400 to uninfected ferrets, no in-vivo anti-influenza-virus activity was observed at the same dosage given 4 times daily for 3 days. The intranasal administration of III-Phos, which was expected to have a more notable in-vivo anti-influenza-virus activity, was examined. III-Phos, whose intranasal absorption had been improved by the modification of III with phosphate ester in rats, inhibited viral replication in the nasal cavity and suppressed influenza-virus-induced fever when administered intranasally to infected ferrets.

This study demonstrates that intranasally administered compounds with anti-influenza-virus activity must permeate the nasal membranes to produce their anti-influenza-virus effect.
Tissue Distribution and Excretion of CDRI-81/470 in Rats
Authors: Nagaraja Nelamangala V , Singh Sheo K , Paliwal Jyoti K , Gupta Ram C
Published: July 2003

Methyl-N[5[[4-(2-pyridinyl)-1-piperazinyl]carbonyl]-1H-benzimidazol-2-yl] carbamate (CDRI-81/470) is a broad spectrum anthelmintic agent, effective against both intestinal and systemic parasitism. Tissue distribution and excretion of CDRI-81/470 were studied in rats after a single oral dose of 100 mg kg−1 CDRI-81/470.

One of the metabolites was identified in pilot studies as its N-decarboxylate derivative and characterized by synthesis. HPLC assay methods for the simultaneous estimation of CDRI-81/470 and its N-decarboxylate derivative in tissues, bile, urine, and faeces were developed and validated. The parent compound was quantitated in all major tissues and organs up to 48 h post-dose. Among the tissues other than serum, the highest concentrations of CDRI-81/470 were found in liver, whereas only trace levels were found in brain. Approximately 3% of the administered dose was excreted unchanged in urine at 120 h post-dose, whereas approximately 7% was recovered in faeces. The contribution of the biliary route for the excretion of parent compound was less than 0.5%. The N-decarboxylate derivative was quantitated in faeces (1–4%) and bile (< 0.1%) but was absent in serum, tissues, and urine. An additional metabolite was isolated from bile and characterized as the pyridinyl-5-hydroxy derivative of CDRI-81/470.

CDRI-81/470 showed rapid absorption and distribution into all major organs and tissues, and underwent extensive metabolism in rats. Two metabolites in bile were identified and characterized by synthesis.
Effect of Rifampin on Plasma Concentrations of Mefloquine in Healthy Volunteers
Authors: Ridtitid Wibool , Wongnawa Malinee , Mahatthanatrakul Werawath , Chaipol Pinyada , Sunbhanich Methi
Published: July 2003

Mefloquine is a 4-quinolinemethanol compound structurally related to quinine. Quinine is mainly metabolized by the cytochrome P450 3A4 isozyme (CYP3A4), whereas rifampin, a potent inducer of CYP3A4, is known to markedly decrease plasma quinine concentration. Our aim was to study the effect of rifampin on the pharmacokinetics of mefloquine, and explore a possible role of CYP3A4 on mefloquine metabolism.

In an open, two-phase crossover study, seven healthy Thai male volunteers received a single oral dose of 500 mg mefloquine alone, or 500 mg mefloquine plus a long-term administration of 600 mg rifampin. Blood samples were collected at specific time points over a 56-day period. Plasma mefloquine and its carboxylic acid metabolite were measured by HPLC for pharmacokinetic analysis. The results indicate that rifampin significantly decreased the area under the plasma concentration-time curve (AUC0-∞) of mefloquine by 68% (P<0.01), maximum plasma concentration (Cmax) by 19% (P<0.01), and elimination half-life (t 1/2) by 63% (P < 0.01), whereas the time to reach Cmax (tmax) of mefloquine was unaffected. The apparent oral clearance (CL) of mefloquine was significantly increased by 281% (P < 0.01). After administration of rifampin, the Cmax of the carboxylic acid metabolite of mefloquine was significantly increased by 47% (P < 0.05), whereas the t 1/2 was significantly decreased by 39% (P < 0.01), and tmax by 76% (P < 0.01). The AUC0-∞ and CL of the mefloquine metabolite were increased by 30% and 25%, respectively, but were not significantly different from the control phase.

The results indicate that rifampin reduces the plasma concentration of a single oral dose of 500 mg mefloquine by increasing metabolism of mefloquine in the liver and gut wall. The CYP3A4 isozyme most likely plays an important role in the enhanced metabolism of mefloquine. Simultaneous use of rifampin and mefloquine should be avoided to optimize the therapeutic efficacy of mefloquine and prevent the risk of Plasmodium falciparum resistance in malarial treatment.
Rapid Identification of Digitalis purpurea Using Near-Infrared Reflectance Spectroscopy
Authors: Kudo Mariko , Watt Robert A , Moffat Anthony C
Published: July 2003

Glycosides from Digitalis are widely used for the treatment of various cardiac conditions. The potential for near-infrared (NIR) spectroscopy as a technique for the rapid identification of Digitalis purpurea was studied. If successful, this method would be advantageous over traditional methods which are destructive and time-consuming.

It was possible to identify D. purpurea from other plants using a Maximum Distance in Wavelength Space statistical comparison method on standard normal variate-corrected, second-derivative spectra. Match values ranged from 1.65 to 2.26 for correct identification and were greater than 112.1 for other plants. It was also possible to discriminate between different plant parts of D. purpurea, with match values ranging from 1.52 to 2.26 for leaves and greater than 29 for other parts of the same plant. The use of correlation coefficients and the Correlation in Wavelength Space methods proved less conclusive, with resulting values for leaves from different plants being very high, and in all but one case, above 0.9. A two-wavelength, nearest neighbours analysis was carried out for de-trended (baseline corrected), standard normal variate-corrected spectra at 1150 and 2160 nm. This resulted in the successful identification of unknown samples.

NIR spectroscopy has the potential for the rapid identification of D. purpurea, and possibly for other natural products of pharmaceutical interest.
In-vitro Antioxidant and In-vivo Photoprotective Effect of Three Lyophilized Extracts of Sedum telephium L. Leaves
Authors: Bonina Francesco , Puglia Carmelo , Tomaino Antonio , Saija Antonella , Mulinacci Nadia , Romani Annalisa , Vincieri Franco F
Published: July 2003

Sedum telephium L. is a medicinal plant used in antiquity to cure many types of inflammatory skin diseases. The leaves (without the external cuticle), are used to promote healing and reduce skin inflammation and pain, and contain various components. We found two major components: flavonol glycosides and polysaccharides, with molecular weight between 13 000 and 13 500 Da. We evaluated the in-vitro antioxidant and in-vivo skin photoprotective effects of three lyophilized extracts obtained from the juice of S. telephium L. leaves: a total lyophilized juice, a lyophilized flavonolic fraction, and a lyophilized polysaccharidic fraction. Two in-vitro models were used: the bleaching of the stable 2,2-diphenyl-1-picrylhydrazyl (DPPH*) radical, and the protective effect against UV-induced peroxidation on phosphatidylcholine multilamellar vesicles, as model membranes. The antioxidant/radical scavenging activity of each lyophilized extract was also assessed in-vivo by determining their ability to reduce UVB-induced skin erythema (monitored by reflectance spectrophotometry) in healthy human volunteers.

The findings of the in-vitro experiments clearly demonstrated that, unlike the lyophilized polysaccharidic fraction, the lyophilized flavonolic fraction and total lyophilized juice possess strong antioxidant/free radical scavenging properties, which are likely due to phenolic compounds. Consistent with these findings, gel formulations of both the total lyophilized juice and, to a greater degree, the lyophilized flavonolic fraction appeared to possess a strong protective effect against UV-induced skin erythema in-vivo, whereas the lyophilized polysaccharidic fraction was completely ineffective.

The in-vitro and in-vivo results suggest that, both the total lyophilized juice and, in particular, the lyophilized flavonolic fraction, but not the lyophilized polysaccharidic fraction of S. telephium L. leaves, have photoprotective effects against UVB-induced skin damage.
Effects of Naturally Occurring Stilbene Glucosides from Medicinal Plants and Wine, on Tumour Growth and Lung Metastasis in Lewis Lung Carcinoma-Bearing Mice
Authors: Kimura Yoshiyuki , Okuda Hiromichi
Published: July 2003

Stilbene glucosides are naturally occurring phytoalexins, found in a variety of medicinal plants. Among the stilbene derivatives, resveratrol 3-O-D-glucoside (piceid) is found in grapes and wine. We studied the effects of stilbene glucosides isolated from medicinal plants and grapes on tumour growth and lung metastasis in mice bearing highly metastastic Lewis lung carcinoma (LLC) tumours. We also studied the inhibitory effects of stilbene glucosides on differentiation of human umbilical vein endothelial cells (HUVECs) to form a capillary network.

Tumour growth in the right hind paw and lung metastasis were inhibited by oral administration of the stilbene glucosides, piceid and 2,3,5,4′-tetrahydroxystilbene-2-O-D-glucoside for 33 consecutive days, in LLC-bearing mice. As the number of CD8+ and NK1.1+ T cells in the spleen was not affected, the inhibitory effects of these stilbene glucosides on tumour growth and lung metastasis could not be explained by natural killer or cytotoxic T lymphocyte activation. Piceid inhibited the DNA synthesis in LLC cells at a concentration of 1000 μm, but not at lower concentrations (10–100 μM). 2,3,5,4′-Tetra-hydroxystilbene-2-O-D-glucoside also inhibited DNA synthesis in LLC cells (IC50 81 μM). In addition, both stilbene glucosides inhibited the formation of capillary-like tube networks (angiogenesis) of HUVECs at concentrations of 100 to 1000 μM.

We suggest that the antitumour and antimetastatic activity of the stilbene glucosides, piceid and 2,3,5,4′-tetrahydroxystilbene-2-O-D-glucoside, might be due to the inhibition of DNA synthesis in LLC cells and angiogenesis of HUVECs.
Effect of Rhazya stricta Decne on Monoamine Oxidase and Cholinesterase Activity and Brain Biogenic Amine Levels in Rats
Authors: Ali B H , Tanira M O M , Bashir A K , Al-Qarawi A A
Published: July 2003

The effect of treatment with the medicinal plant Rhazya stricta Decne, on monoamine oxidase (MAO) and cholinesterase activity, and on the concentration of brain biogenic amines was studied in rats.

R. stricta extract, at doses of 0.2 and 0.5 g kg−1, significantly (P < 0.05-0.01) increased the hepatic and cerebral activity of MAO by 36–127%. The higher doses used (2.0 and 8.0 g kg−1) produced smaller (10–26%) and statistically insignificant increases in MAO activity in liver and brain. Cholinesterase activity in blood, liver and brain was not significantly influenced by treatment with R. stricta. The concentrations of the measured biogenic amines (noradrenaline, adrenaline, 5-hydroxytryptamine and dopamine) were significantly lowered in rats treated with R. stricta.

The observed increase in MAO activity may be responsible for the lowered biogenic amines levels and may, in part, be responsible for the pharmacological effects of R. stricta extract in rats.
Thermal Dependence of Multidrug-resistant-modulator Efficiency: a Study in Anionic Liposomes
Authors: Castaing Madeleine , Loiseau Alain , Dani Michele
Published: July 2003

This study was designed to test the hypothesis that there exists a correlation between the ability of lipophilic drugs to mediate the reversal of multidrug-resistance (MDR) by interacting with the membrane phospholipids and the metabolic level in tissues. The permeation properties of five MDR-modulators were studied by quantifying their ability to induce the leakage of Sulphan blue through unilamellar liposomes, over the temperature range 27–42°C.

The dye leakage induced by a non-ionic detergent (Triton X-100), two calcium blockers (diltiazem and verapamil) and two antiparasitic agents (thioacridine derivative and mepacrine) was temperature-dependent. The permeation process was a co-operative one (1.1 < Hill coefficient < 7.5) and the permeation doses inducing 50% dye leakage (PD50) were 1.5–14.9 mM. The permeation ability of the MDR-modulators (log(1/PD50)) decreased significantly as the net electric charge (z) increased. The passive dye leakage (ΔG < 0) was found to be an endothermic process (ΔH > 0), favoured by an increase in the membrane disorder (ΔS > 0). The apparent enthalpy factor (ΔH50) associated with 50% dye leakage increased with the net electric charge of the compound, and this energetically non-favoured event was entirely offset by the concomitant increase in the entropy factor (ΔS50). The apparent permeation enthalpy (ΔH50) and entropy (ΔS50) showed the lowest values for Triton X-100 (ΔH50 = 7.1 ± 0.53 kJ mol−1, ΔS50=76.9 ± 1.86 J mol−1 K−1), and the highest values for mepacrine (ΔH50 = 79.5±3.80 kJ mol−1, ΔS50 = 306.7 ± 5.97 J mol−1 K−1). When the temperature was increased from 27 to 42°C, the apparent Gibbs free energy (ΔG50) of the dye leakage induced by Triton X-100 decreased by less than 10% of the initial value, and that induced by mepacrine decreased by nearly 40%.

The results provide evidence that in tissues with high metabolic levels and therefore high temperatures, MDR-reversal is likely to be enhanced via favourable drug-membrane interactions controlled by the electric charge of the modulators.
Synergistic Effects of Iontophoresis and Jet Injector Pretreatment on the In-vitro Skin Permeation of Diclofenac and Angiotensin II
Authors: Sugibayashi Kenji , Kagino Midori , Numajiri Sachihiko , Inoue Naoko , Kobayashi Daisuke , Kimura Masayuki , Yamaguchi Masatoshi , Morimoto Yasunori
Published: July 2003

A non-needle syringe (jet injector) was utilized to increase skin permeation of drugs by iontophoresis. Briefly, physiological saline was initially flushed by the injector to make a pore in the stratum corneum of excised hairless rat skin, and the iontophoretic skin permeation of two model compounds, sodium diclofenac and angiotensin II, was followed using a 2-chamber diffusion cell. Constant voltage and constant current iontophoresis treatments were evaluated.

Pretreatment using the jet injector alone resulted in about 13- and 22-fold increases in the steady-state flux of diclofenac and angiotensin II, respectively, through the skin, compared with non-treated controls. Jet injector pretreatment with constant voltage iontophoresis further enhanced skin permeation of diclofenac and angiotensin II, and the enhancement was also greater than that by constant voltage iontophoresis alone. Thus, a synergistic effect was observed. The ratio of enhancement was greater compared with the control. Jet injector pretreatment with constant current iontophoresis, however, did not always yield higher skin permeation of the drugs than injector pretreatment alone, although the lag time was shortened. The difference in the enhancement between the constant voltage- and constant current iontophoresis can be explained by the electric current through the excised skin.

Constant current iontophoresis after a short period of constant voltage iontophoresis with multiple jet injector pretreatments may be the best way to increase drug permeability while preventing severe skin damage.
Colon Delivery Efficiencies of Intestinal Pressure-controlled Colon Delivery Capsules Prepared by a Coating Machine in Human Subjects
Authors: Hu Zhaopeng , Mawatari Shunsuke , Shimokawa Tatsuharu , Kimura Go , Yoshikawa Yukako , Shibata Nubuhito , Takada Kanji
Published: July 2003

Large quantities of pressure-controlled colon delivery capsules (PCDCs) were prepared by a Hicoater-mini pharmaceutical coating machine and colon delivery efficiencies were evaluated in man. Caffeine powder as a model drug was suspended with a polyethylene glycol (PEG) 1000 suppository base at 50°C, and was hardened in no. 0- and no. 2-sized capsular shapes. The capsule-shaped suppositories were coated with 5% w/v ethanolic ethylcellulose (7G grade) solution using the coating machine.

By increasing the coating weight of ethylcellulose from 28.6 ± 1.1 mg to 45.3 ± 0.2 mg, the mean coating thickness of no. 0 PCDCs increased from 56 ± 1 μm to 64 ± 1 μm. With no. 2 PCDCs, the mean coating thickness increased from 50 ± 1 μm to 57 ± 1 μm by increasing the coating weight of ethylcellulose from 8.1 ± 0.5 mg to 11.2 ± 0.3 mg. The no. 0 PCDCs, having a mean ethylcellulose coating membrane thicknesses of 56± 1 μm (type 1) and 64 ± 1 μm (type 2), as well as no. 2 PCDCs, having thicknesses of 50 ± 1 μm (type 3) and 57 ± 1 μm (type 4), were used for in-vivo evaluation in man. After oral administration of test preparations containing 75 mg of caffeine, saliva samples were obtained and salivary caffeine levels were measured by an HPLC method. The first appearance time, Ti, of caffeine in the saliva was used as a parameter for the estimation of the release time of caffeine from PCDCs in the gastrointestinal tract. The mean Ti values of no. 0 PCDCs were 3.3 ± 0.3 h for type-1 and 5.3 ± 0.3 h for type-2 preparations while the mean Ti values of no. 2 PCDCs were 4.3 ± 0.5 h for type 3 and 5.3 ± 0.3 h for type 4. There were good correlations between ethylcellulose coating membrane thicknesses and in-vivo Ti values. A colon arrival time of 5 h was reported in our subjects by gastrointestinal magnetomarkergraphy.

PCDCs having a mean coating thickness of 64± 1 μm for no. 0 capsules and of 57 ± 1 μm for no. 2 capsules were thought to deliver caffeine to the human colon efficiently.
Biodegradable Microparticles with Different Release Profiles: Effect on the Immune Response After a Single Administration via Intranasal and Intramuscular Routes
Authors: Spiers Ian D , Eyles Jim E , Baillie Les W J , Diane Williamson E , Alpar H O
Published: July 2003

In the development of single-dose microparticulate vaccines, identification of the type of protein release profile required to elicit high and sustainable immune responses is important. Microparticles exhibiting different protein release profiles (continuous, pulsatile and plateau) were made by solvent evaporation or solvent extraction methods from biodegradable polymers encapsulating the model antigen, bovine serum albumin (BSA). The immune responses obtained after a single intranasal or intramuscular administration of microparticles were determined, and also after a subcutaneous boost after 11 months.

Microparticles were manufactured with acceptable protein loading and average volume size ranging from 1 to 10 μm. The integrity of BSA extracted and released from microparticles after 2 months incubation was retained. Microparticulate preparations administered by either intranasal or intramuscular routes, evoked rapid, high titre and long-lived (up to 11 months after priming) specific serum IgG responses which were significantly greater than for free BSA. The type of protein release from microparticles had no significant effect on the systemic immune responses. Interestingly, a formulation exhibiting a plateau-release profile was the only microparticulate system capable of inducing significantly greater IgA responses than free BSA after intranasal immunization.

This study shows the benefit of microencapsulation in inducing high and long-lasting systemic immune responses after a single dose by both parenteral and mucosal delivery. We conclude that of the microparticles tested, the longevity and magnitude of humoral responses was not effected by the type of in-vitro protein release profile.
Mitigation of Surfactant Erythrocyte Toxicity by Egg Phosphatidylcholine
Authors: Gould Larissa A , Lansley Alison B , Brown Marc B , Forbes Ben , Martin Gary P
Published: July 2003

Polyoxyethylene alkyl ether surfactants have been shown to have excellent penetration enhancing abilities although they are associated with a high level of local toxicity. We have compared the toxicity of a range of polyoxyethylene alkyl ethers (Brij 96, Brij 76, Brij 56, 10 lauryl ether and 9 lauryl ether) to an anionic surfactant (sodium dodecyl sulphate (SDS)), an ampholytic surfactant (lysophosphatidylcholine) and a cationic surfactant (tetradecyltrimethylammonium bromide (TTAB)), in the presence and absence of egg phosphatidylcholine.

The toxicity of the surfactants or phospholipid/surfactant mixtures was assessed by measuring haemolytic activity. The test samples were incubated with a suspension of red blood cells for 30 min and Drabkin's reagent was used to indicate the amount of haemoglobin released.

All of the polyoxyethylene alkyl ethers, SDS, TTAB and lysophosphatidylcholine exhibited haemolytic activity at concentrations between 0.10 and 0.25 mM. The addition of egg phosphatidylcholine reduced the toxicity for all of the surfactants, with the toxicity of Brij 96 being mitigated to a greater extent than the toxicity of the other polyoxyethylene surfactants examined. The rate of haemolysis induced by Brij 96 or 10 lauryl ether was also reduced by increasing concentrations of phosphatidylcholine. As the phosphatidylcholine content of a mixed surfactant system comprising egg phosphatidylcholine: Brij 96 was replaced by lysophosphatidylcholine and fatty acid, the haemolytic action of the mixture increased markedly.

The results from this study show that the toxicity of surfactants to erythrocytes can be mitigated by the addition of egg phosphatidylcholine. Synthetic surfactants combined with phosphatidylcholine may generate drug delivery systems worthy of more extensive investigation.
The Effects of Carrier Size and Morphology on the Dispersion of Salbutamol Sulphate after Aerosolization at Different Flow Rates
Authors: Zeng Xian Ming , Martin Gary Peter , Marriott Christopher , Pritchard John
Published: July 2003

We have investigated the interdependence of various factors (particle size, surface smoothness, carrier particle shape, inhalation flow rate) on the deposition of a model drug (salbutamol sulphate) after aerosolization from a model inhaler device (Rotahaler).

Different batches of α-lactose monohydrate were prepared to have different particle size, particle shape and surface smoothness. Each batch of lactose was then mixed separately with salbutamol sulphate in a ratio of 67.5:1 (w/w), under similar conditions. Drug deposition from each formulation was investigated using a 4-stage liquid impinger after aerosolization at 28.3, 60.0 and 96.0 L min−1 via a Rotahaler.

At a flow rate of 28.3 L min−1, a large portion of drug particles was not emitted from the inhaler, the % emission varying from 29.6% to 66.6% for all formulations investigated. Drug emission tended to increase with particle size of the carrier whilst fine particle fraction, fine particle dose and dispersibility appeared to increase with decreasing particle size but increasing elongation ratio of the carrier particles. Increasing the flow rate to ***60.0 L min−1 was shown to increase drug emission since >75% total dose was found to be emitted from the inhaler. Again, smaller or more elongated lactose particles resulted in a higher fine particle dose or fine particle fraction of salbutamol sulphate than the coarser carrier, although they produced a similar (analysis of variance P>0.05) drug emission. Increasing the flow rate to 96.0 L min−1 did not increase drug emission. Increasing the flow rate resulted in an increase in the fine particle fraction and fine particle dose of salbutamol sulphate from all formulations. The flow rate of the airstream appeared to play the most important role, followed by particle size and elongation ratio of the carrier particles, with the surface smoothness relatively less significant in determining the deposition of salbutamol sulphate from the Rotahaler.
The Use of a Capillary Rheometer to Determine the Shear and Extensional Flow Behaviour of Nasal Spray Suspensions
Authors: Eccleston Gillian M , Hudson Nick E
Published: July 2003

The rheological profiles of four commercial nasal spray suspensions (Beconase, Flixonase, Nasacort and Nasonex) were compared using rotational viscometry. Two of the nasal sprays (Beconase and Nasonex) were further examined in both shear and extension using a capillary rheometer under conditions similar to those experienced at the spray nozzle (i.e. extremely high shear rates with significant stretching or extensional flow).

In rotation, the shear viscosity fell rapidly with increase in shear rate. Plots of the viscosity derived at the lower shear rates in rotation were extrapolated to include the high-shear rate capillary values. At very high shear rates, the shear viscosity of Beconase was higher than that of Nasonex with the cross-over occurring in the extrapolated region at approximately 10 000 s−1. In the transition region between laminar and turbulent flow (shear rate 6–8 times 104 s−1) there was a minimum in the shear viscosity to less than that of water for Nasonex and similar to water for Beconase, and a plateau region in extensional viscosity for Beconase but not Nasonex. These anomalies were due to the extensive aeration of both samples when sprayed. Whereas Beconase had de-aerated within 30 min of the experiment, Nasonex had not de-aerated completely after six weeks. The very low viscosity at the shear rates at the nozzle imply that it is unlikely that the low viscosity of the spray on delivery to the nose is a key factor in prolonging its residence time.

The extensional viscosity for these rather fluid samples was over 1000-times the shear viscosity (not 3-times as with Newtonian fluids) and both sprays exhibited strain hardening over the range covered. The high extensional stress in the nozzle enables the fluid to form as reasonably sized droplets rather than fine atomized droplets, which rather than settling in the nose, would be prone to redistribution through the normal respiratory function. Both sprays resisted degradation despite the high shear rates and extensional stresses experienced.
Effects of Dosing Time and Schedule on Cisplatin-Induced Nephrotoxicity in Rats
Authors: Kobayashi Minoru , To Hideto , Yuzawa Masayuki , Hakamata Yoji , Higuchi Shun , Tokue Akihiko , Fujimura Akio , Kobayashi Eiji
Published: July 2003

Renal dysfunction induced by a single injection of cisplatin depends on the timing of the dose. However, the effects of repeated administration of cisplatin on time-dependent toxicity have not been evaluated despite the fact that in clinical practice high doses are repeatedly injected at intervals or low doses are administered daily. We studied chrono-nephrotoxicity in rats after weekly or daily cisplatin injections.

Weekly high doses (5 mg kg−1) or daily low doses (1.2 mg kg−1) of cisplatin were injected at four time points (3, 9, 15 and 21 h after the light was turned on (HALO)) for 3 weeks. Changes in body weight after weekly cisplatin administration were independent of the timing of the doses. In the group that received daily cisplatin, the loss in body weight in the 3 HALO group was smaller than in animals receiving injections at 15 and 21 HALO (P < 0.05 and 0.001, respectively). The blood urea nitrogen and serum creatinine levels in the control rats showed a significant circadian change (peak at 15 HALO and trough at 9 HALO), but these parameters were markedly elevated in both trials and their circadian variations were disturbed. In conclusion, cisplatin-induced nephrotoxicity was the lowest at 3HALO compared with other time points of both dose regimens.
Pharmacokinetic Interactions between HIV-1 Protease Inhibitors in Rats: Study on Combinations of Two Kinds of HIV-1 Protease Inhibitors
Authors: Shibata Nobuhito , Matsumura Yasuhiro , Okamoto Hiroyuki , Kawaguchi Yuko , Ohtani Akiko , Yoshikawa Yukako , Takada Kanji
Published: July 2003

The drug interactions between four human immune deficiency virus (HIV-1) protease inhibitors have been characterized by in-vitro metabolic studies using rat liver microsomal fractions and in-vivo oral administration. In this study, a new HPLC analytical method developed by us was used for the simultaneous determination of saquinavir and nelfinavir in rat plasma and microsomes.

The metabolic clearance rates (Vmax/Km) of saquinavir, nelfinavir, and indinavir were 170.9 ± 10.9, 126.1 ± 4.4, and 73.0 ± 2.0 μL min−1 (mg protein)−1, respectively. Ritonavir was the strongest inhibitor with inhibition constants (Ki) of 1.64 μM for saquinavir, 0.95 μM for indinavir, and 1.01 μM for nelfinavir. Nelfinavir was the second strongest inhibitor with Ki's of 2.35 μM for saquinavir and 2.14 μM for indinavir. Indinavir was the third strongest inhibitor with Ki's of 2.76 μm for nelfinavir and 3.55 μM for saquinavir. Saquinavir was the weakest inhibitor for the other three HIV-1 protease inhibitors. After oral co-administration in combination with another HIV-1 protease inhibitor, the AUCs of saquinavir, indinavir, and nelfinavir were significantly increased compared with mono-treatment. The AUCs of saquinavir were increased about 10.1-, 3.1- and 45.9-fold in the presence of indinavir, nelfinavir and ritonavir, respectively. The AUCs of indinavir were increased about 6.8-, 5.9- and 9.4-fold in the presence of nelfinavir, saquinavir and ritonavir, respectively. The AUCs of nelfinavir were increased about 2.2-, 6.6- and 8.5-fold in the presence of indinavir, saquinavir and ritonavir, respectively.

The in-vivo effects observed after co-administration of two kinds of HIV-1 protease inhibitor were not always expected from in-vitro data, suggesting the presence of other interaction processes besides metabolism in the liver. These results provide useful information for the treatment of AIDS patients receiving combination therapy with two HIV-1 protease inhibitors.
Synthesis and in-vitro anticancer evaluation of bistacrine congeners
Authors: Hu Ming-Kuan
Published: July 2003

In the search for potential new anticancer drugs, an efficient synthesis of bis-tetrahydroaminoacridine (bis-tacrine) and its congeners was accomplished by bis-amination of 9-chlorotetrahydroacridine and its congeners under heated conditions.

The critical chlorides were efficiently prepared from o-aminoaromatic acids and cycloketones in-situ in the presence of phosphorus oxychloride. In-vitro cytotoxic evaluation of the compounds was carried out against a panel of 60 human cancer cell lines. Among them, butyllinked bis-tacrine (5b) exhibited the strongest cytotoxic profile with GI50 (concentration causing 50% growth inhibition) values of approximately 0.04-0.08 μM against breast, colon, melanoma and non-small lung cancer cells. Congeners bearing a longer alkyl chain were on average 30- to 100-fold less cytotoxic against these cancer cells. Shorter connecting alkyl chains of bis-tacrine or its congeners dramatically decreased the cytotoxic effects.

Compound 5b has been selected for further biological evaluation of its anticancer profile.
Potential transition state phosphoramidate inhibitors of β-tubulin as antifilarial agents
Authors: Anderson R J , Bendell D J , Hooper M , Cairns D , Mackay S P , Hiremath S P , Jivanagi A S , Badami S , Biradar J S , Townson S
Published: July 2003

Transition state phosphoramidate inhibitors of β-tubulin were designed as potential antifilarial agents.

The reactionof 2-aminobenzimidazole with diisopropyl phosphite and carbon tetrachloride at a low temperature gave the unexpected 1-diisopropoxyphosphoryl-2-aminobenzimidazole, which on heating gave the novel benzimidazole derivative, 2-(diisopropoxyphosphoryl)-aminobenzimidazole. Both products were fully characterized and the synthetic procedure to both compounds was optimized. The procedure was used to prepare the related 5-benzoyl-2-(diisopropoxyphosphoryl)aminobenzimidazole and 5-benzoyl-2-(diethoxyphosphoryl)amino-benzimidazole (1d). In a preliminary trial against Brugia pahangi compound 1d was found to have no antifilarial activity. This lack of activity may be attributed to its extreme insolubility and thus low bioavailability. The synthesis of analogous, more soluble, phosphorothioate-substituted benzimidazoles using the same methods may yield compounds with greater antifilarial activity.
A near-infrared method for the assay of cineole in eucalyptus oil as an alternative to the official BP method
Authors: Wilson Nicola D , Watt Robert A , Moffat Anthony C
Published: July 2003

Eucalyptus oil of British Pharmacopoeia (BP) and European Pharmacopoeia standard must contain not less than 70.0% w/w 1,8-cineole (eucalyptol). The official assay is a freezing-point method which involves the addition of o-cresol to the eucalyptus oil, whereupon the o-cresol and the 1,8-cineole form a solid complex. The assay has several disadvantages and we aim to show that near-infrared (NIR) spectroscopy is an attractive alternative to this method, in that it is simple to use, requires no sample preparation and is potentially as accurate as the traditional method.

Thirty different eucalyptus oil samples were scanned on the FOSS NIRSystems 6500 Rapid Content Sampler using a reflectance vessel as sample presentation method. The cineole content of each sample was determined by the BP method and these reference data were used to construct two calibration equations for cineole content in the oils using Vision software. The mean accuracy for the NIR method differed by 1.01% or less, and the mean bias by ±0.33% or less, compared with the BP method. Calculation of the 95% confidence intervals for the slope and intercept of plots of NIR predicted values against BP method reference values showed that there was no evidence of fixed or relative systematic errors. Tests for short-term and intermediate repeatability were conducted. The standard deviation was 0.83% w/w or less and the coefficient of variation was 1.11% or less. The confidence intervals for both short-term and intermediate repeatability overlapped with that for the BP method, suggesting that there was no evidence for a difference in values obtained by the BP and NIR methods. The range of cineole contents used in the calibrations was extended by incorporating five samples of eucalyptus oil spiked with cineole, and five samples of two essential oils known to have a lower cineole content than eucalyptus oil, to give a range of 52.5 to 99.0% w/w. The mean accuracy decreased to an error of 1.26% or less and the bias to ±0.50% or less. Again, confidence intervals suggested there was no evidence for fixed or systematic errors in the NIR calibrations.

We propose that NIR spectroscopy could be used as an alternative method for the determination of cineole content in eucalyptus oils.