In vitro evaluation of commercially available theophylline sustained release tablets in Pakistan

The dissolution behavior of five commercially available brands of sustained release theophylline
tablets was studied in phosphate buffer solutions of pH 1.2, 4.5, 5.5, 6.0 and 7.5 at 37 °C using the
USP dissolution apparatus II (paddle method). Drug concentration in the samples was determined spectrophotometrically
at 272 nm. For predicting the release characteristics of theophylline from selected commercially
available tablets the data obtained in the dissolution studies was fitted into various mathematic
models defining kinetic parameters of drug release like zero-order rate equation, first-order rate equation,
Hixen-crowell cube root law, Higuchi equation and Korsemeyer-Peppas model. Tablets were subjected to
weight variation test, hardness, drug content and in vitro release studies. The present study revealed that
drug release increases with the increase of pH of the dissolution medium and also varies from brand to
brand. Among the five selected brands, B1 and B4 showed better pH dependency and drug release behaviour.
It has been suggested that possible reasons for difference in dissolution or drug release behaviour
are the difference in the manufacturing techniques and the quantity of hydrophobic excepients used by
different manufacturers, which retard the penetration of dissolution medium and ultimately decreases
availability of drug in the solution.
Colegio de Farmacéuticos de la Provincia de Buenos Aires