Influence of food and hepatobiliary disease on the excretion of josamycin

Sensitive and specific method for the determination of josamycin in human plasma by liquid chromatography-mass spectrometry

A highly sensitive and specific method for the determination of josamycin in human plasma by LC-MS was developed and validated. Josamycin was extracted from human plasma by a single-step liquid-liquid extraction and analyzed by LC-MS via an electrospray ionization interface. Selected ion monitoring was used to detect josamycin and its internal standard. The intra-day precision and accuracy, expressed as C.V. and R.E., ranged from 2.8% to 13.5% and -10.3% to 7.6%, respectively. The lower limit of detection was 0.1 ng/ml and the lower limit of quantitation was set at 1 ng/ml when 0.5 ml of plasma was used. No endogenous interference was observed in human plasma obtained from drug-free volunteers.

Effect of moderate or severe hepatic impairment on clarithromycin pharmacokinetics

The pharmacokinetic and safety profiles of clarithromycin (C) and its 14-hydroxy-clarithromycin (HC) metabolite were determined after a multiple-dose oral clarithromycin regimen (250 mg twice daily for five doses) in six healthy subjects and seven patients with moderate or severe hepatic impairment (Pugh grades B and C). Plasma and urine C and HC concentrations were determined using high-performance liquid chromatography. Hepatic impairment resulted in increased harmonic mean C terminal disposition half-life and mean +/- SD C renal clearance (CLR) compared with normal volunteers (5.0 vs. 3.3 hr and 170 +/- 69 vs. 111 +/- 17 mL/min, respectively). Hepatic impairment also resulted in decreased metabolite peak plasma concentration and area under the plasma concentration-versus-time curve and decreased metabolite/parent concentration ratios compared with normal volunteers. These data suggest that 14-hydroxylation of C was reduced by moderate to severe hepatic impairment. No adverse events were noted in either study group and there were no study-related clinically significant changes in laboratory parameters. The decrease in C metabolic clearance appears to be partially offset by an increase in C CLR, resulting in comparable steady-state concentrations of parent drug. In those indications in which the metabolite may be a necessary element of the antimicrobial activity of C, it would seem prudent to be cautious in using C in patients with moderate to severe hepatic impairment due to reduced production of HC. Otherwise, no dosage adjustment for C appears necessary for subjects with moderate or severe hepatic impairment provided that renal function is not impaired.

High-performance liquid chromatographic analysis of josamycin in serum and urine

A high-performance liquid chromatographic assay for the analysis of josamycin in human serum and urine is presented. The assay involves a simple solid-phase extraction procedure coupled with a phase separation step, separation on a reversed-phase C18 column with UV detection by a multi-wavelength programmable detector. The mobile phase was acetonitrile-0.015 M phosphate buffer, pH 6.0 (5:2) at a flow-rate of 1.2 ml/min. The column temperature was maintained at 35 degrees C. Linear calibration curves over the concentration ranges 0.1-2.0 mg/l (serum) and 0.5-5 mg/l (urine) were obtained with correlation coefficients of 0.9983 and 1.0000, respectively. The relative standard deviations of five replicate samples at the upper and lower limits of each calibration curve were below 7%. The recoveries at the upper and lower ends of the calibration range for serum were 77% and 70%, respectively, and those for urine were 76% and 80%, respectively.