Comparison of in vitro release rates of diclofenac topical formulations using an in-line cell automated diffusion system

Abstract

The in vitro release test (IVRT) is a powerful tool for prediction of the impact of formulation excipients on the drug release profile as well as lot-to-lot uniformity. We have determined and compared the release profile of diclofenac (a non-steroidal anti-inflammatory agent) from marketed topical formulations using an in-line cell automated diffusion system. We describe the advantages of the automated diffusion system along with factors influencing the in vitro release, such as type of membranes and receptor solution. A validated reverse phase-high performance liquid chromatography (RP-HPLC) method at a wavelength of 276 nm in the range of 0.200 to 100.000 µg/mL was used for effective analysis of in vitro release samples, with good sensitivity and precision. A linear relationship was found, with a coefficient of determination (R2) ≥ 0.90 for diclofenac semisolid matrices. Among all similar strength formulations, the maximum release rate was obtained from Volini gel and Voltaren Forte, having 1% w/w and 2% w/w diclofenac, respectively.