Investigation of dissolution behavior of diclofenac sodium extended release formulations under standard and biorelevant test conditions

Background: Dissolution characteristics of four extended release (ER) generic formulations of diclofenac sodium were examined. Aim: The aim of this study was to compare the drug dissolution behavior of diclofenac ER generics to clarify whether the products are characterized by comparable dissolution characteristics under the applied test conditions. Methods: The investigations were performed in the USP apparatus 2 and in the new biorelevant dissolution stress test device. Results: The experiments yielded striking differences between the generic formulations. Applying USP apparatus 2 it was noticed that the dissolution profiles of the products were distinctly affected by the stirring rate. Using the biorelevant dissolution stress test device susceptibility of the products to biorelevant stresses was observed. Change of pH within the experiments reduced the dissolution rates of all formulations and distinctly influenced their dissolution characteristics. Conclusion: The study demonstrates clearly the divergences in the dissolution behavior among the generic ER formulations of diclofenac sodium. The observed susceptibility of the tested dosage forms toward biorelevant stress bears in our interpretation the risk to cause unwanted fluctuations in drug plasma concentration profiles.