For couples wanting to avoid or delay pregnancy, female contraceptives have been the only hormonal choice. Researchers have been looking for a male hormonal contraceptive for around 20 years and it seems like an injection may be a solution. This would allow men and women to share the responsibility of birth control equally.
The jab aims to reduce sperm counts of over 15 million per milliliter to fewer than one million per milliliter to significantly reduce the chance of pregnancy in partners. The injection consists of 200mg of norethisterone enanthate combined with 1000mg of testosterone undecanoate, administered every eight weeks. It has been found to be 96 percent effective, tested on 320 participants, men aged 18-45 and their female partners aged 18-38, both without any known fertility problems. Of those, 95.9 out of 100 continuing users experienced suppressed sperm counts to the desired levels within 24 weeks of the first injection and during the efficacy phase of up to 56 weeks (that is the phase in which couples relied solely on the injection for birth control), four pregnancies were reported among the female partners, a rate of 1.57 percent.
The side effects of the shot may still need to be improved, as there are concerns about adverse effects including acne, injection site pain, increased libido and mood disorders. The study was terminated early following the recommendation of an external safety review committee. In total, 20 men dropped out of the study and eight had not recovered normal sperm counts after a year.
Although the exact formula may not yet be pinpointed, the results of this study show promise that the discovery of a male contraceptive jab may be on the horizon.
The Journal of Clinical Endocrinology & Metabolism