Contraceptives are methods or means of preventing pregnancy. There have been a lot of developments in the field of contraception but the world population is growing at a tremendous pace. A large proportion of pregnancies are unwanted. This indicates a need for the development of more reversible methods of preventing pregnancy.
Issues of mutual trust
A lot of surveys have confirmed the willingness of men to use contraception for preventing pregnancy, whereas in certain cases there was unwillingness due to religious or cultural reasons. The obvious contraceptive like a condom, when used by their male partner, is acceptable to women. But if a male has to use an oral contraceptive, the female partner should trust her male partner; because a failure of male contraceptive will affect the female reproductive health.
Evolution of male contraceptives
The hormonal pills for males are still in the research stage and are not available commercially. There are many reasons associated with difficulty in the development of such a pill. Male hormonal contraception is based on testosterone or gonadotropin inhibition, which may result in azoospermia (0 sperm/ml), severe oligospermia (≤1 million sperms/ml), or oligospermia (<3 million sperms/ml) among users. To achieve azoospermia (absence of sperm cells in the semen), a very high dose of testosterone is required which will then suppress the production of LH (luteinizing hormone) and FSH (follicle-stimulating hormone) from the pituitary gland or GnRH (gonadotropin-releasing hormone) from the hypothalamus. A WHO (world health organization) trial was conducted using the drug testosterone enanthate and was found to be effective in producing azoospermia. It causes weight gain, reduction in testicular size, and a decrease in serum HDL cholesterol. Other oral formulations of testosterone have also undergone a lot of trials. Methyltestosterone is available as an oral preparation, but it causes liver damage and hepatomas on prolonged use. So it is not safe for use as an oral contraceptive. The other formulation is testosterone undecanoate; its blood levels depend on its consumption with a fatty meal and a thrice-daily dose. So it becomes an unreliable and poor choice for oral intake.
Contraceptive pills for men – how do they work?
Because of adverse effects on prolonged use of testosterone, other combinations were tried. These included combination therapy with GnRH antagonists and progestins. Progestins inhibit the secretion of gonadotropins from the pituitary. Many progestins have been combined with testosterone to improve its contraceptive effect by augmenting the suppression of gonadotropins. A combination of oral progestin (etonogestrel) and monthly intramuscular injections of testosterone decanoate over a period of one year was found effective in inducing azoospermia or oligospermia below 1 million per ml. The combination therapy of testosterone and progestin (levonorgestrel, etonogestrel, norethindrone, or medroxyprogesterone) results in azoospermia rates of almost 90%. Hence, research is being directed in this line and it is felt that these combinations are most likely to result in a clinically useful contraceptive method.
GnRH antagonists can suppress FSH and LH production within hours of administration and inhibit gonadotropin secretion. Longer-acting GnRH antagonists are being developed and are undergoing scientific trials. A long-acting formulation of the GnRH antagonist abarelix causes gonadotropin suppression for a duration of about 1 month. It has been found to cause serious allergic reactions, and so its use on a larger scale could not be done. The other GnRH antagonist, any line is very effective in suppressing gonadotropins for up to 15 days after subcutaneous injection. Its side effects are not significant.
The final word
There are a lot of single-agent and combination regimes undergoing phase II and phase III trials. Their long-term effects are yet to be known. It is likely that in near future, a suitable male contraceptive pill would be produced, which will be effective and free of side effects.
