Calcium Channel Blocker as a Male Contraceptive - Brief Article - Statistical Data Included

0 Comments | Family Practice News, Feb 1, 2000 | by Kate Johnson

TORONTO -- The calcium channel blocker nifedipine holds promise as a reliable, reversible male contraceptive, according to Dr. Susan Benoff.

"We've definitively proven that this drug produces a reversible male infertile state. And it has very few side effects--perhaps some headaches, some bleeding of the gums. Even men who are normotensive are not made hypotensive by taking this drug," she said at the conjoint annual meetings of the American Society for Reproductive Medicine and the Canadian Fertility and Andrology Society.

Dr. Benoff, director of the molecular biology laboratories of the department of obstetrics and gynecology at North Shore University Hospital, Manhasset, N.Y, explained that researchers there have uncovered the mechanism by which nifedipine immobilizes sperm.

"It has nothing to do with the pharmacologic action of the drug; rather, it works by changing the cholesterol content of the sperm. If you load sperm with cholesterol, you can make them nonfunctional," said Dr. Benoff, who is also associate professor of obstetrics and gynecology and cell biology at New York University.

She and her associates discovered the contraceptive side effects of nifedipine by accident after noting that a number of male patients in their fertility clinic were taking the drug.

"We would never have guessed this, because when we looked at the patients' semen analyses they looked perfectly normal, and yet they were giving us fertilization failure. But when we switched them to other hypotensive medication, sperm function returned," she said.

This mechanism, which produces infertility within i month of taking the drug and can be reversed within 3 months of discontinuing it, could be the basis for the elusive male contraceptive pill.

"If we can develop a drug that can specifically increase the sperm's cholesterol, the sperm will then be unable to bind to the zona-pellucida, which is the first step of gamete interaction; unable to penetrate; and unable to fuse with the oocyte and form a viable embryo," Dr. Benoff explained.

She said this is a concept that has never been suggested before in the field of contraceptive research, even though it is well known that sperm must lose cholesterol before binding with the zona-pellucida.

But it could take some time, perhaps 5-to years, before a nifedipine-based product is marketed specifically for contraception, she said.

"Drug companies do not perceive the male as wanting to play a role in family planning, and the cost of clinical trials and the development of a new product are expenses that do not seem to be a priority right now," Dr. Benoff noted.