Pharmacokinetics and bioavailability of a new testosterone gel formulation in comparison to Testogel® in healthy men

Abstract This randomized, open‐label, multiple‐dose three‐way cross‐over study compared the pharmacokinetics of a new testosterone gel formulation in two strengths, testosterone gel 1% and testosterone gel 2% (FE 999303), with Testogel® in 11 testosterone‐suppressed healthy men. Subjects received one of six treatment sequences; 50 mg of testosterone was administered once daily for 7 consecutive days, with different treatments separated by washout‐periods of 6–9 days. Testosterone gel 1% and testosterone gel 2% displayed greater relative bioavailability (2.6‐ and 1.6‐fold, respectively) than Testogel on Day 1, which persisted, to a smaller extent, on Day 7. Initial absorption was highest and most rapid for testosterone gel 1% and 2%, showing apparent first‐order absorption kinetics. Maximum serum concentrations (C max ) were 6.25 and 2.97 ng/mL, respectively, occurring ∼5–6 hours post‐application on Day 1 versus C max of 1.71 ng/mL after ∼24 hours with Testogel, showing apparent zero‐order absorption kinetics. Similar differences were observed on Day 7. All treatments appeared to reach approximately the same steady‐state level within the first 24 hours. No application‐site skin reactions occurred with any preparation. In conclusion, the new testosterone formulation showed higher bioavailability, and the ability to deliver more testosterone in a smaller volume.