Osmotically controlled-delivery of metoprolol in man: in vivo performance of Oros systems with different durations of drug release.

In vivo absorption from 19/190 and 19/285 metoprolol Oros drug delivery systems has been assessed by measuring plasma drug concentrations after single administration of the systems to six healthy volunteers. The initial in vitro release rate for both Oros preparations was 19 mg/h but they contained 190 or 285 mg of metoprolol fumarate. The plasma concentration-time profiles for both Oros dosage forms were consistent with an extended duration of release and absorption from the gastrointestinal tract. Analysis of the plasma level data indicated that the rate and duration of in vivo absorption closely mirrored the in vitro release behaviour of the 19/190 and 19/285 systems, but the in vivo profiles showed a 1-2 h initial delay. The administration of the 19/190 system on two occasions to the same six volunteers indicated that in vivo release of drug from this Oros preparation was reproducible.