HPLC-MS determination of clindamycin in human serum after intravaginal administration of clindamycin phosphate vaginal gel

Objective: To establish an accurate and sensitive HPLC-MS method for the determination of clindamycin serum concentrations in healthy Chinese female volunteers after a single dose and multiple doses of 5.0 g clindamycin phosphate vaginal gel. Methods: Mosapride was used as internal standard. The human serum samples were alkalized with 0.1 mol·L~(-1) sodium hydroxide solution, extracted with acetic ether and analysed by HPLC-MS method. The seperation was carried on a Hypersil ODS2 column (5μm, 4.0mm×200mm) at 25℃, and eluted with acetonitrile-5 mmol·L~(-1) ammonium acetate solution (55: 45 ) at a flow rate of 0.8 mL·min~(-1). The detection was performed with positive ion SIM mode of clindamycin ([M+H]~+, m/z 425) and mosapride ([M+H]~+, m/z 422). Results:The detection limit of clindamycin in serum was 0.5 ng·mL~(-1), with a good linearity in the range of 0.5-320ng·mL~(-1)(r=0.9998). The average recovery was more than 88%, and RSD for inter -day and intra-day were both less than 9.0%. The IS and clindamycin were in good separation. Conclusions: The method is proved to be sensitive, accurate, convenient and suitable for the pharmacokinetic study of clindamycin after intravaginal administration of clindamycin phosphate vaginal vaginal gel in healthy women.