Effects of skin washing on systemic absorption of testosterone in hypogonadal males after administration of 1.62% testosterone gel

Abstract

Objective:The impact of washing on the pharmacokinetics, systemic absorption and residual testosterone on the skin after application of a 1.62% testosterone gel was investigated in an open-label, randomized, three-way crossover study in hypogonadal men.Research design and methods:Twenty-four hypogonadal men (total testosterone <300 ng/dL) applied 5 g of 1.62% gel (81 mg testosterone) once daily to the shoulders/upper arms for 7 days during each of three consecutive treatment periods. On the 7th dosing day of each period, the skin was washed (soap/water) at one of the following times: 2, 6, or 10 hours post-dose. Pharmacokinetic serum samples were collected at baseline, and on days 6 (no washing) and 7 (with washing) of each treatment period. Skin stripping for determination of residual testosterone was also performed on days 6 and 7. A single location on the application site was stripped a total of 10 times. Testosterone was extracted from the tape strips using ethanol, and concentrations were determined using high performance liquid chromatography with diode array detection (HPLC-UV).Main outcome measures:Testosterone Cmax, AUC0–24, average concentration over the dosing interval (Cav), and safety were assessed.Results:Washing at 2 and 6 hours caused a 10–14% decrease in AUC0–24 and Cav, but not Cmax. Washing 10 hours after gel application had no effect on Cmax, AUC0–24, or Cav. Skin washing decreased the mean amount of testosterone remaining on the skin surface by at least 81%.Conclusions:Washing the site of gel application as soon as 2 hours after application had little impact on bioavailability and was effective in reducing residual testosterone on the skin. This finding may be important to prevent secondary transfer.Study limitations:The experimental conditions using uniform timing and procedures for dose administration and washing may not fully reflect real world circumstances.Clinical Trial Registration NCT Numbers:Study was not registered (first subject enrolled 22 December 2006)