An alternative high-performance liquid chromatographic method for determination of clindamycin in plasma.

A simple, sensitive, selective and reproducible method based on a reversed-phase chromatography was developed for the determination of clindamycin in human plasma. Clindamycin was separated from the internal standard (phenobarbital) on a Luna C18 column (250 x 4.6 mm, 5 mm particle size: Phenomenex, USA), with retention times of 5.6 and 14.2 minutes, respectively. Ultraviolet detection was set at 210 nm. The mobile phase consisted of a solution of 0.02 M disodiumhydrogenphosphate (pH 2.8) and acetonitrile (76:24 v/v), running through the column at a flow rate of 1.0 ml/min. The chromatographic analysis was operated at 25 degrees C. Sample preparation (1 ml plasma) was done by a single step liquid-liquid extraction with water saturated ethylacetate. Calibration curves in plasma at concentrations of 0.25, 0.5, 1.0, 2.0, 4.0, 8.0 and 16.0 microg/ml were all linear with correlation coefficients better than 0.999. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 15% (% coefficient of variations: %CV). Good accuracy was observed for both the intra-day and inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +/- 15%). Limit of quantification was accepted as 0.07 microg using 1 ml plasma sample. The mean recovery for clindamycin and the internal standard were greater than 95%. The method was free from interference from fosmidomycin, including commonly used drugs, antimalarials and antihelminthics. The method appears to be robust and has been applied to a pharmacokinetic study of clindamycin in a patient with malaria following oral doses of clindamycin at 10 mg/kg body weight given twice daily for 7 days.