Kinetics of rate controlled rectally administered ranitidine to male volunteers

Ranitidine hydrochloride solution was given rectally to six healthy volunteers by means of an osmotic pump (Osmet^®) at a zero-order rate for 8 h. Quite constant steady-state drug concentrations were achieved in the range of 64–123 ng/ml plasma (meanC _ss: 100.6 ng/ml). The mean absorption time was 0.45 h (range 0–1.02 h), indicating that absorption was not always instantaneous. It is concluded that the Osmet^® system together with the rectal route offer the possibility for achieving steady-state concentrations of ranitidine, enabling the determination of pharmacodynamic effects. In addition, the rectal route can be considered as an alternative to oral and intravenous administration.