Analysis of the phamacokinetics of ribostamycin in serum and perilymph of guinea pigs after single and multiple doses.

The pharmacokinetics of ribostamycin in serum and perilymph of guinea pigs was studied after a single s.c. injection of 400 mg/kg or 14 daily injections of the same dose. The repetitive administration of ribostamycin did not produce functional impairment of the kidney and ototoxicity was slight. The pharmacokinetic data were analysed by non-linear least mean squares regression. Ribostamycin did not accumulate in either serum or perilymph after multiple dosing. The half-life of the drug in perilymph was 15.8 h after a single injection, but 7.6 h after the last of 14 injections. The area under the ribostamycin concentration in perilymph against time curve was also reduced after multiple dosing. These changes were found to be due to a marked increase in the rate of transfer of the drug from perilymph to serum after multiple dosing.