Pharmacokinetics of L/105, a new rifamycin, in rats and dogs, after oral administration.

The absorption and tissue distribution of a new rifamycin, L/105, which chemically is 4-deoxy-4'-methylpyrido [1',2'-1,2]imidazo [5,4 C] rifamycin SV, were studied in rats after oral administration of 100 mg/kg. This study showed that L/105, contrary to what was observed for rifampicin, was practically not absorbed: neither serum nor significant tissue levels were evidenced. Also in dogs, after oral administration of L/105 in a single dose (25 mg/kg) and a multiple dosage (10 mg/kg/day, for 8 days), no traces of the compound were detected in the serum. The elimination was investigated in the rat: the highest recovery of L/105 (more than 50% of the administered dose) was in feces after 72 h, hardly any traces were found in urine.