Clarithromycin bioequivalence study of two oral formulations in healthy human volunteers

To assess the bioequivalence of two tablet formulations of clarithromycin (Clamicin 500 mg from Medley Indlistria Farmaceutica, Brazil, as the test formulation, and Biaxin 500 mg from Abbott Industries, USA, as the reference formulation).

A single 500 mg oral dose of each formulation was administrated in 24 healthy volunteers of both sexes (12 males and 12 females). The study was conducted open, randomized, two-period crossover design with a 7-day interval between doses. The plasma concentrations of clarithromycin were quantified by reversed phase liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using multiple reaction monitoring (MRM) method. 14-hydroxyclarithromycin concentration was estimated semiquantitatively as equivalent of clarithromycin/ml. The precision of the method was evaluated using calibration curves and plasma quality control samples. The pharmacokinetic parameters calculated for both compounds included: AUC(0 - 48h), AUC(0 - infinity), Cmax, Cmax/AUC(0 - 48h), Tmax, T1/2 and Ke.

Standard curves of clarithromycin in plasma were linear in the range of 0.05 microg x ml(-1) to 10 microg x ml(-1) (r > 0.999). The limit of quantification was 5 ng/ml. Within- and between-run plasma quality control CV were 5.8% and 15.7%, respectively. Inaccuracy within- and between-runs were 14% and 17%, respectively. 90% CI for clarithromycin geometric mean AUC(0 - 48h), AUC(0 - infinity) and Cmax ratios (test/reference) were: 8.7% - 103.1%, 89.4% - 103.7% and 85.4% - 99.6%, respectively, and for hydroxyclarithomycin were 80.3% - 108.6%, 80.1% - 110.1% and 85.4% - 112.6%, respectively.

The method described for the quantification of charithomycin and its main metabolite is accurate and sensitive. Clamicin was considered bio-equivalent to Biaxin based on the rate and extent of absorption. Since these were no significant differences in the bioequivalence determined using the pharmacokinetic parameters of either clarithromycin or 14-hydroxyclarithromycin, we suggest that future bioequivalence trials of this drug may be performed by quantifying clarithromycin only.