In Vitro Permeation Characterization of the Analgesic Ibuprofen and the Sunscreen Oxybenzone

Ibuprofen, one of the mostly prescribed nonsteroidal anti-inflammatory drugs (NSAIDs), has been proposed as a topical medication for secondary prevention against skin damage induced by sunburn. The objective of this study was to characterize transmembrane permeation of ibuprofen and sunscreen oxybenzone across poly(dimethyl siloxane) (PDMS) membrane. In vitro diffusion studies were carried out at 37° and 45°C, using a series of ibuprofen and oxybenzone samples, either individually or in combination. Concentrations of ibuprofen and oxybenzone in the receptor compartment for up to 6 h were measured using a high-performance liquid chromatography (HPLC) assay. Ibuprofen and oxybenzone permeated across the PDMS membrane in all diffusion studies. When applied individually, permeation percentages of ibuprofen and oxybenzone ranged from 1.0 to 4.1% and from 13.2 to 25.8%, respectively. When applied in combination, permeation percentages of ibuprofen and oxybenzone were 0.3-1.4% and 7.8-24.3%, respectively. Transmembrane permeation was significantly suppressed when both compounds were present concurrently. High temperature promoted the diffusion process of oxybenzone; a linear correlation was also observed between oxybenzone concentration and its permeation. The proposed permeation enhancement between ibuprofen and oxybenzone was not observed from this study. The potential transdermal interaction and systemic absorption from concurrent application of topical analgesics and sunscreens thus requires further systematic evaluation.