Nonlinear Pharmacokinetics of Topical Flurbiprofen Gel in a Phase I Study Among Chinese Healthy Adults

Introduction PDX-02 (Flurbiprofen sodium) is a topical nonsteroidal anti-inflammatory drug in gel formulation for local analgesia and anti-inflammation. A Phase I clinical trial was conducted to assess the safety, tolerability, and pharmacokinetics of single and multiple doses of PDX-02 gel in Chinese healthy adults. Methods The trial comprised three parts: (1) a single-dose ascending study with three dose levels (0.5%, 1% to 2% PDX-02 gel) applied on a 136 cm 2 skin area; (2) a multiple-dose study with either 1% or 2% PDX-02 gel applied on a 136 cm 2 skin area for 7 consecutive days; and (3) a high dose group with 2% PDX-02 gel on an 816 cm 2 skin area and a frequent multiple dose group with 2% PDX-02 gel on a 272 cm 2 skin area four times a day for 7 consecutive days. The safety, tolerability and pharmacokinetics of the PDX-02 gel were evaluated in each part. Results A total of sixty participants completed the trial, with all adverse events recovered and all positive skin reaction being transient and recovered. The overall absorption of topical PDX-02 gel was slow with a mean peak time exceeding 9 h. The elimination rate remained consistent between dose groups. A less-than-dose-proportional nonlinear pharmacokinetics relationship was observed within the studied dose range, and this is likely due to the autoinduction of skin first-pass metabolism. Conclusion The topical PDX-02 gel showed favorable safety and tolerability in both single and multiple dosing studies, with a less-than-dose-proportional nonlinear pharmacokinetics observed.