[Comparison of roxithromycin bioavailability of a conventional and a dispersible tablet formulation]

Following oral administrations of a single dose of 150 mg roxithromycin dispersible tablet (formulation A, a new formulation for clinical trial) and conventional tablet (formulation B, purchased from the market) to each of 10 healthy male volunteers in a randomized crossover design, the plasma levels of active drug at different times were determined by a microbial assay with Micrococcus luteus CMCC (B) 28001 and the plasma concentration-time profiles were obtained. The Tmax values of formulation A and B obtained were 1.7 +/- 0.9 and 3.7 +/- 1.6 h, the Cmax values were 4.97 +/- 1.17 and 2.04 +/- 1.26 micrograms.ml-1 and the AUC0-->infinity values were 62.2 +/- 11.9 and 35.0 +/- 16.9 micrograms.h.ml-1, respectively. Surprisingly, the relative bioavailability of formulation B was found to be only 59.8% +/- 32.6% (P < 0.01). The low bioavailability of the latter formulation was attributed to poor release of roxithromycin in the gastric site, which was proposed as a key factor to influence drug absorption. Other related factors were also discussed.