Bioequivalence study of clindamycin phosphate injection (Clinott-P) in Thai healthy volunteers

Generic clindamycin given intramuscularly, should have identical active ingredient(s), strength, and demonstrable bioequivalence to those of original product. The aim of this investigation was to compare the bioavailability of a single, intramuscular injection, of 2 ml. of 300 mg. of a generic clindamycin (Clinott-P) and the original preparation (Dalacin C).

A randomized, double-blinded, crossover study was conducted. Twenty-four healthy males were recruited at Siriraj Hospital and randomized to receive a single intramuscular injection of either Clinott-P or Dalacin C. Treatment was followed by a two-week washout period. Blood samples were collected at 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12 and 24 hours after the injection. Plasma samples were analysed for clindamycin by a validated HPLC method at the Faculty of Pharmaceutical Sciences, Chulalongkorn University.

Twenty-four volunteers enrolled in and completed the study. They exhibited an average height of 167.92 cm (SD = 5.82), weight of 60.10 kg (SD = 7.36), body mass index of 21.27 (SD = 1.73) and normal blood chemistries. The Cmax of Clinott-P was 3.94225 microg/ml at Tmax 1.75 hours and of Dalacin C, 3.6847 microg/ ml at Tmax 2.09 hours. The AUC0-24 of Clinott-P was 16.32 +/- 6.13 micro.hr/ml and Dalacin C was 17.24 +/- 7.46 microg.hr/ml. Ninety percent confidence intervals of the mean ratios (test/reference) of log transformed of Cmax (93.07-123.43%), AUC(0-24) (82.58-112.31%) and AUC(0-inf), (81.54-110.06%) were all within the standard range (80-125 %) for bioequivalence study. Tenderness after injection around the deltoid area was assessed blindly and was found to be slight (visual basic score < 5) and presented for one or two days after the injection.

The two brands of clindamycin exhibit comparable pharmacokinetic parameters and volunteers exhibited slight and tolerable tenderness at the injection site.