Largest ever trial brings male contraceptive jab a step closer

Scientists in China have completed the largest ever trial to assess the effectiveness of a male hormonal contraceptive, which showed it achieved a 99 per cent success rate over the two and a half years of the study. Researchers at the National Research Institute for Family Planning (NRIFP) in Beijing injected over 1,000 healthy, fertile men with a formulation of testosterone undecanoate (TU) in tea seed oil for thirty months, temporarily halting sperm production during the trial, but with fertility returning to normal levels afterwards. The findings, reported in the Journal of Clinical Endocrinology and Metabolism, raise hopes that an effective and reversible hormonal contraceptive regime for men may yet be possible.

1,045 Chinese men with normal medical histories and between the ages of 20-45 - all of whom had fathered at least one child in the preceding two years - were enlisted in the study, with two thirds completing the trial. They were given a monthly 500mg testosterone injection, which reduced the production of two regulatory brain chemicals, follicle-stimulating hormone (FSH) and luteinising hormone (LH); these disrupted sperm production. Only one in 100 men fathered a child while receiving the treatment, putting its effectiveness on a par with female contraceptive injections and the Pill. Sperm production returned to normal levels after four to six months in all but two of the participants, and with none of the short-term side effects that have beleaguered previous research on male hormonal contraceptives, such as mood-swings and lowered sex drive.

Scientists have been searching for a male hormonal contraceptive for almost two decades, and China has invested heavily in reproductive technology, however progress has been hampered by a lack of interest in large-scale trials by pharmaceutical companies, and by persistent survey results indicating that women would not trust men to use hormonal contraceptives reliably. Doctor Yi-Qun Gu, of the NRIFP in Beijing explains that the current study shows that 'for couples who cannot, or prefer not to use only female-oriented contraception...a male hormonal contraceptive regimen may be a potential, novel and workable alternative'.

However, despite these encouraging results, questions about the effectiveness of the treatment in non-Chinese men, as well as its long-term effects need to be ironed-out before the contraceptive could become widely available, potentially in the next five years. According to Elaine Lissner of the Male Contraception Information Project (MCIP) in San Francisco, 'testosterone alone, which was used in this study, is not considered effective enough; studies in Caucasian men add a progesterone hormone to the regimen'.

Dr Gu has also cautioned that more research is needed to ascertain the long-term safety of the treatment, 'with a focus on cardiovascular, prostate and behavioural safety'.