Kinetics of absorption and elimination of ofloxacin in humans after oral and rectal administrations

Ofloxacin pharmacokinetics have been studied in four healthy subjects after a single oral or rectal dose, each of 200 mg. For the oral dose t _max was about 2 h, C _max 1·96±0·56 μ g/ml and AUC _1–15 15·22  μ g/ml.h. Two‐phase elimination pharmacol kinetics were observed for the oral dose, t_1/2 for the rapid elimination phase was 3·3 h and for the slow phase 10 h. With the rectal dose t _max was 6 h, C _max 0·71±0·44 μ g/ml and AUC _0–15 7·58  μ g/ml.h. The relative rectal bioavailability ( AUC rectal/ AUC oral) was 49·8%.%Elimination rate of the rectal dose was generally slow ( t_1/2=9 h), an observation attributable to the sustained‐release effect of the rectal suppository base, PEG 6000. The indication is that the rectal formulation cannot be substituted totally for the oral without first increasing the rectal dose; the 200 mg suppository can however be employed as a follow‐up therapy to the oral dose in certain situations.