An in-vitro comparison of controlled release aminophylline tablets: Phyllocontin Continus and Pecram

It has been suggested that two controlled release preparations containing aminophylline, Phyllocontin Continus and Pecram, are clinically equivalent and are therefore interchangeable. In this study, an in-vitro evaluation of the two preparations was completed using the British Pharmacopoeia dissolution apparatus, initially using water and then an acid/buffer medium to provide a similar pH environment to that within the gastrointestinal tract. Similar release profiles were found when water was used as the dissolution medium, with very little variation between tablets within each group. Good fits were obtained for dissolution-controlled release and diffusion-controlled release models. When the acid/buffer solution was used as the dissolution medium a reduction in the rate of release was observed with Phyllocontin. It was predicted that if this was repeated in-vivo then differences in the peak plasma levels between the two formulations would be seen, although these may be masked by the other variables encountered.