[Dissolution rates and bioavailability of phenytoin preparations (author's transl)].

The dissolution rates of various commercially available oral phenytoin preparations were determined in vitro and compared with the in vivo data for the bioavailability obtained from volunteers in a subchronic study. There is a correlation between the described in vitro method and the classical parameters of a bioavailability study. There are significant differences between the preparations tested. It is shown that the results of the in vitro test give high information about the bioavailability of phenytoin even after chronic administration. Therefore a simple method for standardisation of phenytoin preparations for oral use is available in the field of quality control.