Reexamination of Pharmacokinetics of Oral Testosterone Undecanoate in Hypogonadal Men With a New Self‐Emulsifying Formulation

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Abstract
Many hypogonadal men prefer oral testosterone (T) treatment. Oral T undecanoate (TU) is available in many countries, but not in the United States. We aimed to assess the pharmacokinetics of oral TU in a new self‐emulsifying drug delivery system formulation. Pharmacokinetics studies were conducted in 3 parts: 12 hypogonadal men were enrolled in 2 centers for a 1‐day dosing study; 29 participants were enrolled from 3 centers for a 7‐day dosing study; and 15 participants were enrolled from 1 center for a 28‐day dosing study. Serial blood samples for serum sex hormone measurements by liquid chromatography–tandem mass spectrometry were drawn for up to 36 hours after oral TU administration. Mean serum T levels (Cavg) after oral dosing of T 200 mg as TU twice daily with food were within the adult male range in most participants in the 1‐, 7‐, and 28‐day dosing studies but were much lower in the fasting state. The dose‐proportional increase in Cavg of serum T after oral T 300 mg twice daily resulted in more participants with supraphysiologic serum T levels. In the 28‐day study, trough serum T reached a steady state at day 7. Serum dihydrotestosterone and estradiol levels tracked serum T concentration. Dihydrotestosterone‐testosterone ratios increased 3‐fold after oral TU administration. Oral T 200 mg twice daily as TU in a new SEDDS formulation may be a viable therapy for hypogonadal men.

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