Relative bioavailability of rimantadine HCl tablet and syrup formulations in healthy subjects

Twenty healthy male subjects completed an open-label randomized crossover design to assess the bioavailability of 100 mg of rimantadine HCl in tablet and syrup forms relative to an oral solution. Blood samples were drawn and rimantadine plasma concentrations were determined by a GC-MS method. The maximum plasma concentration (Cmax), the time to Cmax (tmax), the area under the plasma concentration-time curve (AUC), and k were compared among treatments using an analysis of variance and the Hauck-Anderson test for bioequivalence. The Hauck-Anderson test was satisfied when the syrup and solution were compared. The relative bioavailability of the syrup was 96%. Both Cmax and AUC were significantly (p less than 0.05) increased (23 and 17%, respectively) when the tablet was compared with the solution. The relative bioavailability of the tablet was 117%. This outcome was unusual and could not be explained. However, this was not anticipated to be of clinical consequence since the majority of the safety and efficacy of rimantadine HCl was established using a tablet.