Stability and in vitro release profile of enalapril maleate from different commercially available tablets: possible therapeutic implications.

Stability of enalapril maleate formulations can be affected when the product is exposed to higher temperature and humidity, with the formation of two main degradation products: enalaprilat and a diketopiperazine derivative. In this work, stability and drug release profiles of 20 mg enalapril maleate tablets (reference, generic and similar products) were evaluated. After 180 days of the accelerated stability testing, most products did not exhibit the specified amount of drug. Additionally, drug release profiles were markedly different from that of the reference product, mainly due to drug degradation. Changes in drug concentration and drug release profile of enalapril formulations are strong indicators of a compromised bioavailability, with possible interferences on the therapeutic response for this drug.