Prediction of Systemic Exposure of Ketoprofen Tapes by In Vitro Release Test and Pharmacokinetic Model Analysis: Comparison between Brand-name and Generic Formulations

Topical dermatological formulations of non-steroidal anti-inflammatory drugs (NSAIDs) are reported to show their pharmacological effect partially through the systemic circulation, and to induce systemic side effects. However, pharmaceutical equivalence and pharmacokinetic bioequivalence between brand-name and generic products are not required. Therefore, we aimed to predict systemic drug exposure from brand-name and nine generic ketoprofen tapes. In vitro release profiles were examined using the paddle-over-disk method, then analyzed by the W. I. Higuchi equation incorporating an initial burst effect. Pharmacokinetic parameters were estimated from observed release profiles and the reported time-plasma concentration profile of the brand-name product. Plasma concentration profiles of generic products were predicted from the observed release profiles and the pharmacokinetic parameters of the brand-name product. In vitro release profiles differed markedly, and estimated release rates for initial burst effect and at 24 hours ranged from 4.20 to 88.75% and from 45.27 to 95.83%, respectively. The predicted plasma concentration profile of each product reflected its release profile, and estimated C_max ranged from 61.70 to 290.30 ng/mL (0.46-to 2.15-fold vs. brand-name product). Generic products were classified into three types, i.e., systemic exposure comparable with, higher than and lower than that of brand-name product. C_max was predicted to increase with enhanced skin permeability for all products, but the increase rates differed among products. These results suggest that safety and efficacy differ between brand-name and generic ketoprofen tapes. Healthcare professionals should carefully monitor systemic side effects, especially when switching from brand-name to generic products for which higher systemic exposure is predicted.