Comparison of the Pharmacokinetics of Two Dosage Regimens of Linezolid in Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis Patients
Background and Objectives
For the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB), potent new drugs are urgently needed. Linezolid is a promising drug, but its use is limited by adverse effects with prolonged administration of 600 mg twice daily. In order to reduce its adverse effects and maintain efficacy, we investigated whether linezolid in a reduced dosage resulted in drug serum concentrations exceeding a ratio of the in vitro minimum inhibitory concentration (MIC) to the area under the serum concentration-time curve (AUC) over 24 hours (AUC24) [AUC24/MIC] of >100.
Patients and Methods
This open-label, prospective pharmacokinetic study evaluated two doses (300 and 600 mg) of linezolid in MDR-TB patients, who received linezolid as part of their treatment. They received linezolid 300 mg twice daily for 3 days, followed by 600 mg twice daily. Blood samples taken at predefined intervals for measuring serum linezolid concentrations were processed by a validated liquid chromatography-tandem mass spectrometry procedure. The AUC24/MIC ratio was used as a predictive model of efficacy. Adverse effects of linezolid, including peripheral neuropathy, were evaluated by clinical and laboratory assessments.
Eight patients were included in this study. The median duration of linezolid treatment was 56 days (interquartile range [IQR 44-82] days), with a median cumulative dose of 51000 mg (IQR 33 850-60 450 mg). The median linezolid AUC over 12 hours (AUC12) values were 57.6mg ·h/L (IQR 38.5–64.2 mg•h/L) with the 300mg dose and 145.8mg•h/L (IQR 101.2–160.9mg•h/L) with the 600mg dose. The AUC24/MIC ratios were 452 (IQR 343-513) with the 300mg dose and 1151 (IQR 656-1500) with the 600mg dose. Linezolid was well tolerated.
Seemingly effective serum concentrations were reached after 3 days of administration of linezolid 300 mg twice daily, i.e. the AUC24/MIC ratio was at least 100 in 7 of 8 patients. Larger numbers of patients should be studied to confirm the efficacy of the linezolid 300 mg twice-daily dosage in MDR-TB or XDR-TB treatment.
KeywordsMinimum Inhibitory Concentration Linezolid Antituberculosis Drug Mutant Prevention Concentration Perfect Colour
The purified linezolid drug substance was kindly provided by Pfizer Inc. (New York, NY, USA). This study was financially supported by Stichting Beatrixoord Noord-Nederland (Groningen, the Netherlands). The authors have no conflicts of interest that are directly relevant to the content of this study.
- 28.Zyvoxid®: prescribing information. Bridgewater (NJ): Pharmacia USA, 2006 Apr 20 [online]. Available from URL: http://www.health.gov.il/units//pharmacy/trufot/alonim/2192.pdf [Accessed 2010 Jun 18]
- 32.Harmelink IM, Alffenaar JWC, Wessels AMA, et al. A rapid and simple liquid chromatography-tandem mass spectrometry method for the determination of linezolid in human serum. Eur J Hosp Pharm 2008; 14(1): 5–8Google Scholar