Disposition of 3-(N-piperidinomethylarino)methyl-rifamycin SV (FCE 22250) in rats

After rats being given ig FCE 22250 5, 10 and 25 mg.kg-1, the plasma peak times (Tmax) were 12-14 h, the max plasma concentrations (Cmax) were 3.0, 5.6 and 12 micrograms.ml-1 respectively, and the half-lives of elimination (T1/2) were 24-26 h. The apparent volumes of distribution of the three doses were about 1 L.kg-1, suggesting that FCE 22250 in blood and in tissue was balanced. Total body clearance rate of each of the three doses was 29 ml.kg-1.h-1. The ig absolute bioavailability ranged from 69-84%. Its distribution in rats was as follows: the highest in liver, next in lung and then in fat, kidney, intestine, spleen, lymphaticode, heart, muscle, testis, the lowest in brain. It was eliminated mainly via the bile with feces. The human serum protein binding rate of FCE 22250 was 96.2%. It was shown that the rate was not correlated with drug concentration in serum under our experimental conditions.