Context: Hormonal male contraceptive regimens effectively and reversibly suppress sperm production, but there are few large-scale efficacy studies.
Objective: The safety, contraceptive efficacy, reversibility, and feasibility of injectable testosterone undecanoate (TU) in tea seed oil as a hormonal male contraceptive was assessed.
Design: This was a multicenter, phase III, contraceptive efficacy clinical trial.
Participants: A total of 1045 healthy fertile Chinese men were recruited throughout China into the study.
Intervention(s): Injections of 500 mg TU were administered monthly for 30 months. A definition of severe oligozoospermia (< or =1 x 10(6)/ml) was used as a criterion of spermatogenic suppression and as the threshold for entering the contraceptive efficacy phase.
Main outcome measure(s): The primary outcome was pregnancy rate in the partner. Other outcomes include: semen parameters, testis volumes, reproductive hormone levels, and safety laboratory tests.
Results: Forty-three participants (4.8%) did not achieve azoospermia or severe oligozoospermia within the 6-month suppression phase. A total of 855 participants entered into the efficacy phase, and 733 participants completed monthly TU treatment and follow-up. There were nine pregnancies in 1554.1 person-years of exposure in the 24-month efficacy phase for a cumulative contraceptive failure rate of 1.1 per 100 men. The combined method failure rate was 6.1%, comprising 4.8% with inadequate suppression and 1.3% with postsuppression sperm rebound. No serious adverse events were reported. Spermatogenesis returned to the normal fertile reference range in all but two participants.
Conclusions: Monthly injection of 500 mg TU provides safe, effective, reversible, and reliable contraception in a high proportion of healthy fertile Chinese men.