Investigation of the Correlation Between Plasma Concentration of Linezolid Antibiotic and Treatment Response and Adverse Reactions

Study Overview
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Brief Summary
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Linezolid is the second line agent in the treatment of MRSA and PRSP infections, and it is also the drug of choice for VRE infections. It can be an alternative option against multidrug resistant tuberculosis and non-tuberculosis mycobacterium. However, Patients who receive more than 2 weeks of treatment duration and who have renal dysfunction or severe cirrhosis may prone to experience anemia, thrombocytopenia, and leukopenia. Long-term use may also result in lactic acidosis, peripheral neuropathy and optic neuropathy due to mitochondrial toxicity. Thus, this study will analysis the medical charts in National Taiwan University Hospital (NTUH) from 2011 to 2016 to get the population demographics who use linezolid and analysis the occurrence rate of myelosuppression, neuropathy and lactic acidosis. Simultaneously, the investigators also use therapeutic drug monitoring (TDM) to prospectively evaluate the association of linezolid blood concentration and clinical efficacy and safety. The result of this study will provide physicians more information to prevent concentration-dependent adverse effects.

Detailed Description
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The increasing resistance of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and penicillin-resistant Streptococcus pneumoniae (PRSP) has caused significant medical issue. With limited antimicrobial agents available, it has been an increasing challenge in infection control and disease treatment. Linezolid is the second line antibiotics in the treatment of MRSA and PRSP infections, and it is also the drug of choice for VRE infections. It can be an alternative against multidrug resistant tuberculosis and non-tuberculosis mycobacterium. Linezolid has almost 100% of bioavailability. It has excellent tissue penetration. It metabolized via non-enzymatic oxidation. Two major metabolites, aminoethoxyacetic acid (chemical name) and hydroxyethyl glycine (chemical name), are final forms before excreted through kidneys. Even though the manufacturer does not recommend dosing adjustment for patients with renal or hepatic dysfunction, recent studies demonstrated accumulation of linezolid and 2 metabolites in the body. Patients who receive more than 2 weeks of treatment duration and who have renal dysfunction or severe cirrhosis may present higher plasma linezolid concentration. Patients may experience anemia, thrombocytopenia, and leukopenia under long-term use of linezolid. However, there is lack of study on lactic acidosis, peripheral neuropathy, and optic neuropathy due to mitochondrial toxicity. This study has two parts. This study will analysis the medical charts in NTUH from 2011 to 2016 to get the population demographics who use linezolid and the occurrence rate of myelosuppression, neuropathy and lactic acidosis. Then, followed by a prospective study which aim is to monitor the plasma peak and trough concentration of linezolid (total and free drug) and 2 metabolites by different sample collecting method (plasma, dry blood spot; DBS). If clinical necessity, the investigators may also monitor tissue fluid concentration. Clinical response and toxicity were monitored by liquid chromatography (LC) analysis. The investigators plan to evaluate the association between plasma concentration and toxicity including bone marrow suppression, peripheral neuropathy, and lactic acidosis. It is important to determine if dose adjustment in patients with renal and/or hepatic dysfunction is required. Simultaneously, the investigators want to develop DBS method which can ease patients' uncomfortable sense and simplify the drug monitor process. The result of this study will provide physicians more information to prevent concentration-dependent adverse effects.

Official Title
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Investigation of the Correlation Between Plasma Concentration of Linezolid Antibiotic and Treatment Response and Adverse Reactions

Conditions
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Myelosuppression, Lactic Acidosis, Peripheral Neuropathy

Participation Criteria
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Eligibility Criteria
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Retrospective study 1. Adults (age > 20 year old) with linezolid treatment (oral or intravenous) in National Taiwan University hospital medical charts record from 2011 to 2016. 2. Patients with linezolid treatment for 3 days or above Prospective study Adults (age > 20 year old) are going to start with linezolid treatment (oral or intravenous) due to gram positive infection, multidrug resistant - tuberculosis (MDR-TB) or nontuberculous mycobacterium (NTM) infection. Keeping follow up in National Taiwan University Hospital Exclusion Criteria: Retrospective study 1. Patients without baseline complete blood count (CBC) data (RBC or Hb, WBC, platelet) before linezolid treatment. Prospective study 1. Patients with severe disease status (assess by clinicians) might die within 2 days or treatment duration less than 2 days

Ages Eligible for Study
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Minimum Age: 20 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Linezolid TDM (prospective)<br>Adult patients received linezolid at NTUH. This prospective cohort study will draw blood from every patient to measure the linezolid blood concentration. After blood concentration analysis by high pressure liquid chromatography (HPLC), the investigator will report the concentration to clinicians and dose adjustment is judged by clinician (not the investigators). | |
| Linezolid observation (retrospective)<br>Adult patients received linezolid at NTUH. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinical efficacy | Clinical efficacy definition: Cure: biological eradication or clinical improvement. (Biological eradication: Eradication of bacterial culture prior to study drug) (Clinical improvement: White blood cell (WBC), C reactive protein (CRP) back to normal range (WBC: 3500 - 9000/mm3; CRP: < 1 mg/dL) or without sepsis symptom (body temperature, pulse, heart rate returned to normal)) Intermittent cure: same bacteria culture positive (with same minimum inhibitory concentration (MIC) data) within 2 weeks after linezolid treatment ends. Failure: persistent bacteria culture after linezolid treatment or unresolved clinical sign and symptoms. Indeterminate outcome: loss of follow up or discontinue linezolid due to adverse drug reaction | Observation periods: entire linezolid treatment course until 30 days after the completion of treatment, loss of follow up, death or December 2020 (up to 4 years). | 
| Safety - thrombocytopenia | Definition of thrombocytopenia: platelet count < 100,000/mm3 and platelet count of < 75% of the baseline counts. | Observation periods: entire linezolid treatment course until resolution of side effect, loss of follow up, death or December 2020 (up to 4 years). | 
| Safety - anemia | Definition of anemia: Hemoglobin (Hb) < 10 g/dL and Hb level of < 75% of the baseline level. | Observation periods: entire linezolid treatment course until resolution of side effect, loss of follow up, death or December 2020 (up to 4 years). | 
| Safety - leukopenia | Definition of leukopenia: WBC count < 3000/mm3 and WBC count of < 50% of baseline count. | Observation periods: entire linezolid treatment course until resolution of side effect, loss of follow up, death or December 2020 (up to 4 years). | 
| Safety - lactic acidosis | Definition of lactic acidosis: Definite lactic acidosis: lactic acid > 4 mmol/L and blood potential of hydrogen (pH) value < 7.35 Probable lactic acidosis: lactic acid > 4 mmol/L without or not achieved pH value data | Observation periods: entire linezolid treatment course until resolution of side effect, loss of follow up, death or December 2020 (up to 4 years). | 
| Safety - peripheral neuropathy | Definition of peripheral neuropathy (PN): Definite PN: with nerve conduction velocity test (+) Probable PN: patient reported symptoms | Observation periods: entire linezolid treatment course until resolution of side effect, loss of follow up, death or December 2020 (up to 4 years). | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Pharmacokinetics,adverse events, Linezolid, Therapeutic drug monitoring, Myelosuppression, Lactic acidosis, Peripheral neuropathy