Investigation of a novel preparation of testosterone decanoate in men: pharmacokinetics and spermatogenic suppression with etonogestrel implants.

We have investigated the pharmacokinetics and effects on the male reproductive axis of a novel preparation of testosterone decanoate (TD) with a progestogen implant. Twenty healthy Chinese men were administered TD (400 mg intramuscular 4 weekly) with two subcutaneous (SC) etonogestrel implants. Trough testosterone concentrations rose with repeated administration. Peak concentrations 1 week after the fourth injection were 31 +/- 2 nmol/liter. Both LH and FSH were rapidly suppressed and continued to fall during treatment. Spermatogenesis was also suppressed, to