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* To whom correspondence should be addressed. E-mail: page{at}u.washington.edu.
Objective: Oral androgen development has been hampered by the rapid metabolism of orally administered testosterone (T) and low bioavailibility. The addition of the 5alpha-reductase inhibitor dutasteride (D) to oral T in oil dramatically improves concentrations of serum T. In this study we evaluate the absorption of oral T+D, comparing nanomilled T (NmT+D) versus T dissolved in oil (Capmul, CpT+D) as nanomilling might offer a simpler, more practical means of oral T administration given the limited solubility of T in oil. Methods: Twelve normal men were administered leuprolide on Day -14 to suppress endogenous T biosynthesis and pretreated with D to block 5alpha-reductase. Once hypogonadal, subjects were sequentially administered 200 and 400 mg doses of CpT+D and NmT+D in the fasted and fed state. Serum T and dihydrotestosterone (DHT) were measured: pre-dose, 0.5,1,2,3,4 6,8,10,12 and 24 hours after each dose. Results: Two weeks after leuprolide administration T levels were below the normal range. A 400 mg dose of either formulation of oral T+D increased mean serum T above the lower limit of the normal range for 8-10 hours. Food had minimal effect on the PK parameters of the NmT+D formulation, but decreased the Cmax for CpT+D. Serum DHT remained below the normal range throughout the study period with both formulations. No significant changes in liver function tests or other adverse events were observed. Conclusions: A 400 mg dose of either oral T+D formulation normalized serum T for 8-10 hours and suppressed DHT. NmT allows for tablet formulation and its pharmacokinetics were not affected by food, demonstrating the feasibility of oral nanomilled T as promising and practical twice-daily therapy for the treatment of male hypogonadism.
Key words: Androgen
Andropause
Hormone
5alpha-reductase
dihydrotestosterone
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