Constraints in the development of contraceptives for men.

Considerable efforts have been made to develop a male contraceptive and the studies have provided very useful information in this field. At least five different strategies to develop a male contraceptive have been pursued, namely: inhibition of sperm production, interference with sperm function, interruption of sperm transport, prevention of sperm deposition, and prevention of sperm-egg interaction. Of all these approaches, inhibition of sperm production by using androgens either alone or in combination with progestins have given the most encouraging results. A number of clinical trials substantiate that it is indeed possible to have a reversible, effective and safe hormonal method of contraception. A postmeiotic and epididymal approach to interfere with sperm function or the secretory and metabolic processes of the epididymis is another attractive option of male contraceptive development. A number of chemical compounds have been identified which interfere with sperm function in the epididymis without affecting sperm production, however, the compounds evaluated so far were found to be toxic. Interruption of sperm transport through the vas either by vasectomy or percutaneous intravasal injection of liquids which form cure-in-place plugs is also an attractive option. However, reversibility of the methods is of concern in their wide scale use. The major constraint in developing a long-acting male contraceptive seems to be the need for greater investment for product development. The clinical trials for evaluating the efficacy and safety of the new products and formulations stretch over several years and require enormous financial commitment. Nevertheless, the long-term gain of having a long-acting reversible contraceptive for men is far greater than the financial commitments over few years. Male attitude towards using methods of family planning is much more favourable than originally believed. The pharmaceutical industry as well as the health care providers therefore have a greater responsibility. For early development of a contraceptive for men, it is essential to increase investment and simplify the drug regulatory procedures. The advent of newer technologies coupled with the convergent efforts of scientists will certainly make it possible to have an effective, safe and reversible male contraceptive in the near future.