Quality Evaluation of Diclofenac Formulations Manufactured in DR Congo

Abstract

The purpose of this study was to evaluate the quality of three generics of 50 mg diclofenac sodium (DS) tablets manufactured and marketed in DR Congo in comparison to the original formulation Voltarene® from Novartis Pharma. Drug content and drug release were respectively determined by HPLC and UV spectrophotometry before storage and at 3 and 6 months of storage in the accelerated-aging conditions of temperature (40°C) and relative humidity (75%) recommended by the WHO for tropical climate areas. Before storage, only generic 2 contained the correct amount of active pharmaceutical ingredient (API). Generics 1 and 3 did not comply with established limits for API, one was overdosed (Generic 1) and one underdosed (generic 3). None of the generics resisted to stress conditions with respect to the API content. Moreover, all generics failed the dissolution tests when they were submitted to tropical climate simulation. Differences to explain the different dissolution profiles were searched with 1H NMR that gives a complete profile of the formulation (API and excipients) and infrared spectroscopy which evaluates the overall distribution of the API in the tablets, on the initial samples. Generic 1 contained the acid form of diclofenac instead of its sodium salt, and generic 2 a mixture of acid and salt forms. Generic 3 displayed a poor DS distribution in the tablets. Taken together, our data demonstrated that the three generics analyzed were substandard.