Bioavailability of oral testosterone in males

Area of Science:

• Endocrinology
• Pharmacokinetics
• Androgen Metabolism

Background:

• Oral testosterone administration presents bioavailability challenges.
• Testosterone undecanoate ester is a common formulation for testosterone replacement therapy.
• Dietary factors can influence the absorption of oral medications.

Purpose of the Study:

• To compare the oral bioavailability of free testosterone versus testosterone undecanoate ester.
• To evaluate the effect of formulation (crystalline vs. arachis oil) on testosterone undecanoate absorption.
• To determine the impact of a high-fat meal on the absorption of both testosterone forms.

Main Methods:

• Twenty-six healthy males received single oral doses of free testosterone or testosterone undecanoate ester (in crystalline form or arachis oil).
• Each participant was tested under fasting conditions and after a high-fat breakfast.
• Serum testosterone concentrations were measured serially for 24 hours post-dose.

Main Results:

• Free testosterone administration resulted in a significant and reproducible increase in serum testosterone levels.
• Testosterone undecanoate ester was effective only when formulated in arachis oil.
• A high-fat meal enhanced the bioavailability of the testosterone ester but had minimal impact on free testosterone absorption.

Conclusions:

• Oral testosterone bioavailability can be significantly improved through pharmaceutical formulation, particularly using arachis oil for the undecanoate ester.
• Dietary fat enhances the absorption of oral testosterone undecanoate.
• Optimized oral formulations may achieve adequate serum testosterone levels for substitution therapy.