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 (R 2) ≥ 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.

Excipients play a very important role in the release pattern of an active pharmaceutical ingredient from topical semisolid dosages forms, and their physical and chemical properties can influence the release. The aim of this paper was to provide a validated, sensitive, and reproducible method to assess the in vitro release rate of an antifungal drug (Terbinafine) from controlled drug delivery systems (cutaneous and film-forming solution) and to prove product sameness. The samples obtained from in vitro testing were analyzed through a high performance liquid chromatographic (HPLC) system coupled with UV spectrometer at a wavelength of 283 nm. A Franz diffusion cell (FDC) system was used for the dissolution test. We recorded the drug release from the formulation for 6 hours. The release rate obtained from cutaneous and filmforming solutions were compared statistically to depict the sameness. The results met the relevant acceptance criteria (i.e., 90% confidence interval, falling within the limits of 75-133%) as defined in the scale-up and post-approval changes (SUPAC-SS) guidance. The obtained results confirm the competence of the IVRT method for the assessment of product sameness.