Relative bioavailability of ketoprofen 20% in a poloxamer-lecithin organogel.

PURPOSE: The bioavailability of a single, topically applied, 200-mg dose of ketoprofen (delivered in a ketoprofen 20% gel) relative to a single 50-mg oral dose in healthy volunteers was studied. METHODS: This was an open-label crossover study. The subjects were randomized to receive an oral 50-mg ketoprofen capsule or a single topical dose of ketoprofen 20% in a poloxamer-lecithin organogel (PLO). Treatment was followed by a one-week washout period. Blood samples were collected at intervals up to 10 hours after administration, and plasma ketoprofen concentrations were determined by high-performance liquid chromatography with ultraviolet or mass spectrometry detection. Noncompartmental pharmacokinetic values were obtained after each dose, and relative bioavailability was calculated. RESULTS: Eight healthy volunteers enrolled in and completed the study. Topical absorption of ketoprofen was highly variable among the subjects over the 10-hour sampling period. The median oral maximum plasma concentration (Cmax) exceeded the topical Cmax by nearly 200-fold (4.15 versus 0.021 microg/mL) (p = 0.001). The median relative bioavailability of topical ketoprofen was 0.48%, with individual subjects' values ranging from 0.18% to 2.1%. CONCLUSION: The relative bioavailability of ketoprofen was low and highly variable when the drug was administered as a single dose in a PLO-based ketoprofen 20% gel.