[RU 28965, a new semi-synthetic macrolide. Bioavailability and pharmacokinetic profile after oral administration]

The plasma concentration of RU 28965, a new semisynthetic macrolide, was monitored for 24 h after single 400 mg oral doses in 8 healthy volunteers. Four tablet formulations were compared in a 4 X 4 latin square design, to assess the influence of micronization and enteric coating on bioavailability. Plasma samples were assayed for unchanged RU 28965 using HPLC. Extent of absorption was equivalent for all four formulations. Micronization did not significantly affect absorption characteristics, while enteric coating resulted in slower absorption. In the second part of the study, plasma concentration was monitored for 72 h after a single oral dose of two 150 mg non-coated, non-micronized tablets in another group of 12 subjects. The following pharmacokinetic parameters were found (m +/- sem) : cmax = 11.8 +/- 0.3 microgram.ml-1, AUC = 132 +/- 17 microgram.ml-1.h, t 1/2 = 12 +/- 0.5 h.