Absorption kinetics of cyclosporin in the rat

Cyclosporin was administered (6 mg kg-1, i.v.) over 15 min, or (10 mg kg-1) by gavage, to two groups of 5 rats. Following i.v. infusion, cyclosporin exhibited triphasic behaviour with mean +/- s.e.m. disposition half-lives of 9.0 +/- 1.3 min, 4.0 +/- 0.5 h and 16.0 +/- 1.7 h. Following oral administration, peak blood concentration (Cmax) of 1290 +/- 93 ng mL-1 was reached after 5 h, when cyclosporin absorption essentially ceased. The absolute bioavailability (F) of cyclosporin was 24.0%. Standard laboratory rat chow consisting of 2% corn oil did not appear to alter cyclosporin absorption kinetics.