Dermatopharmacokinetic bioequivalence study of two types of topical patches containing loxoprofen sodium

This study evaluated the bioequivalence of two types of topical loxoprofen patches, LX-A and LX-P, in healthy Chinese volunteers through a dermatopharmacokinetic approach.Based on a pilot study, this study was designed as an open-label, self-controlled trial in 20 males. Subjects received application of two 3.2 x 3.2 cm(2) pieces of LX-A and LX-P patches on their backs at randomly assigned positions simultaneously. Stratum corneum (SC) samples were taken with adhesive stripping tapes prior to patch application and at 20 hours and 24 hours postdose following removal of each loxoprofen patch, respectively. Bioassay was performed with a validated high performance liquid chromatography-tandem mass spectrometry method. Bioequivalence was evaluated through a power model on the total amount of loxoprofen at each post-application point and on the percentage change of SC loxoprofen content between the two time-points.Mean (± standard deviation) total amount of SC-sampled loxoprofen was similar between LX-A and LX-P at 20 hours (38,722 ± 7,171 ng vs. 39,309 ± 9,688 ng) and 24 hours (36,638 ± 8,149 ng vs. 37,426 ± 9,029 ng) post-administration. The corresponding point estimate (90% confidence interval, 90%CI) of LX-P to LX-A was 1.00 (0.92, 1.09) and 1.02 (0.93, 1.12), respectively. In addition, the 24 hour/20 hour ratio for SC content of loxoprofen was statistically comparable between LX-A and LX-P, with both the point estimate and the 90% CI falling into the range of (0.80, 1.25).Our study indicated that LX-P and LX-A are two bioequivalent topical formulations of loxoprofen.