Dissolution Rates of Phenytoin and Phenobarbital from Commercial and Hospital Pharmacy-Made Tablets

Abstract

The in vitro dissolution rates of phenytoin were compared between commercial and hospital pharmacy-made tablets by the modified beaker method of Levy and Hayes.Six out of 7 lots of the commercial tablets released 56.0-67.5% phenytoin in 90 min., compared with only 52.7 % in one lot. The dissolution rates of phenytoin from three different lots of the tablets showed considerable variation at the initial stage. when the test fluids (pH 1.2) were replaced by buffer solutions (pH 7.5) of three formulae, the dissolution rates of phenytoin from tablets in each medium differed markedly. Remarkable changes in the dissolution rates were observed when the commercial tablets were aged at the room temperature for one year.The dissolution rates of phenobarbital from tablets were much faster than those of phenytoin and all lots of tablets showed release, at least 85 % of the drug, within 30 min. It can be generalized that the rates of phenobarbital from the hospital tablets were faster than the commercial ones.