Testosterone undecanoate: a new orally active androgen.

Oral testosterone undecanoate (TU) in arachis oil has been evaluated with a view to its possible use as a means of androgen replacement therapy. A single 100 mg dose was found to elevate plasma androgen levels and urinary 17-ketosteroid excretion in 6 normal men. Ninety mg/day and 60 mg/day doses taken by a hypogonadal man resulted in sustained levels of androgen which appeared physiological when measured by radioimmunoassay without chromatography. However, upon separation of the steroids by chromatography it was found that much of the androgen present was in fact dihydrotestosterone not testosterone. Both TU and dihydrotestosterone undecanoate were detected in plasma by gas chromatography and it is suggested that the ester is absorbed as such from the intestine and the unesterified steroid subsequently released by hydrolysis. The convenience of oral administration, the resulting prolonged elevated plasma androgen levels and the probable lack of deleterious effects on the liver may render oral TU of value where androgen replacement therapy is indicated.