Effect of relative humidity and ageing on drug release. Part 2: Experimental phenytoin sodium capsules.

In this study the effect of ageing and relative humidity on the release rate of phenytoin sodium was investigated for an experimental capsule formulation. Phenytoin sodium capsules containing lactose as the excipient were kept in 75 and 95% relative humidities, for 8 weeks, and the variances in the in vitro dissolution profiles of the active substance were observed. In vitro dissolution results were also evaluated kinetically. In general, it was observed that there was a decrease in the in vitro dissolution rate after storage at 95% relative humidity.