Determination of Clindamycin in Human Plasma by LC-MS/MS

A LC-MS/MS method for determination of clindamycin in human plasma was developed. After protein precipitation with acetonitrile, the analyte and internal standard (I.S.), diphenhydramine, were separated on a Shim-pack VP-ODS analytical column using the mobile phase of V (methanol)∶ V (10 mmol•L^-1 ammonium acetate (containing 0.25% formic acid))=55∶45 at a flow rate of 0.4 mL•min^-1. Detection was carried out by electrospray positive ionization mass spectrometry in the multiple reaction monitoring (MRM) mode. The MRM transitions of m/z 425.2→126.3 and m/z 256.2→167.3 were used to quantify clindamycin and I.S., respectively. Clindamycin and I.S. are eluted at 1.77 min and 1.79 min, respectively. The calibration curve is linear over the concentration range of 0.030 0-10.0 mg•L^-1 with the lower limit of quantitation (LLOQ) 0.030 0 mg•L^-1. Inter- and intra-day relative standard deviations are both less than 6%, and the relative errors are within ±6%. The mean extract recoveries are (101.1 ± 2.6)%. In the stability studies, clindamycin in plasma is found to be stable under various storage conditions. It is a rapid, sensitive, selective and reliable method for the determination of clindamycin in human plasma. The method is successfully applied to a pharmacokinetic study in healthy volunteers after oral administration of 300 mg clindamycin.