Pharmacokinetics And Relative Bioavailability Of Absorbed Testosterone After Administration Of A 1.62% Testosterone Gel To Different Application Sites In Men With Hypogonadism

ObjectiveTo determine the pharmacokinetics, bioavailability, and safety of a new formulation (1.62%) of testosterone gel that produces eugonadal serum testosterone levels with use of a lower amount of gel than the currently available 1% gels.MethodsIn an open-label, randomized, 3-way crossover study, 36 male patients with hypogonadism applied 5 g of 1.62% testosterone gel (81 mg of testosterone) once daily to the abdomen, to the upper arms/shoulders, or alternating between both sites per an established schedule for7 days. Serum levels of testosterone, dihydrotestosterone, and estradiol were measured and used to compare the pharmacokinetics and bioavailability of the 3 treatments.ResultsEach application method produced average serum testosterone concentrations within the eugonadal range (300 to 1,000 ng/dL), and steady-state testosterone concentrations were achieved after 2 days of gel application to either the abdomen or the upper arms/shoulders. When testosterone gel was applied to the abdomen, approximately 30% to 40% lower bioavailability (based on area under the serum concentration-time curve from 0 to 24 hours) was observed in comparison with application to the upper arms/shoulders. The 1.62% testosterone gel was found to be safe and well tolerated in men with hypogonadism.ConclusionAlthough lower testosterone bioavailability was observed after abdominal application of 1.62% testosterone gel in comparison with application to the upper arms/shoulders, application to either site yielded eugonadal levels of serum testosterone. (Endocr Pract. 2011;17:574-583)