Blood Pressure Drug Shows Potential as Male Oral Contraceptive
Oct. 4, 1999 (New York) -- New research suggests that a drug used to treat high blood pressure may be useful as a male contraceptive. The intriguing finding is the result of observations of reversible infertility in men taking the calcium channel blocker Procardia (nifedipine).
At the recent annual meeting of the American Society of Reproductive Medicine, Susan Benoff, PhD, and colleagues reported that among men who came into a clinic for an infertility problem, those taking the drug had an increase in the cholesterol content of their sperm. This increase interferes with the sperm's ability to undergo a crucial phase of fertilization but does no permanent damage. Benoff is associate professor of obstetrics/gynecology and cell biology at the New York University School of Medicine, North Shore University Hospital in Manhasset, N.Y.
"This would be a perfect contraceptive for the male because he could take this drug and it affects only the sperm's ability to fertilize an egg, and that's what we want it to do," co-author Grace M. Centola, PhD, associate professor of obstetrics/gynecology at the University of Rochester (N.Y.) Medical Center, tells WebMD.
Prior studies have indicated that Procardia, which blocks calcium from entering cells, performs the same function in sperm. The new research indicates that this calcium-blocking effect actually leads to increased cholesterol in the sperm. The high cholesterol level makes the sperm's outer surface rigid, therefore preventing it from penetrating and fertilizing the egg.
To prove this, Benoff and colleagues examined the production of cholesterol from the sperm in the presence or absence of Procardia for 5 or 24 hours. In unexposed samples, the cholesterol was found to be significantly reduced. In contrast, the samples exposed to Procardia had greater cholesterol content.
"In looking more closely, the only common factor was that some of the men were on nifedipine. Everything else in their sperm -- their sperm count, their sperm motility [and] morphology -- was normal, but these sperm were not able to undergo [normal fertilization]," Centola says. The findings suggest the possibility that nifedipine and similar drugs may have potential as reversible forms of male contraception.
Centola says men whose sperm were studied had been on Procardia for various lengths of time, so further study will be necessary to determine how quickly it interferes with sperm action. "Interestingly enough, this research shows that when men are taken off nifedipine their sperm becomes functional and totally fertile within three months," Centola says.
Surprisingly, the increase in cholesterol seen in the sperm has not been seen in other cells in the body. Also, although the drug is a blood-pressure lowering agent, it does not lower pressure adversely in men with normal blood pressure.
Centola says future studies will examine this issue further to measure the impact of individual doses of Procardia or other calcium channel blockers on sperm and also look more closely at how quickly after discontinuing the medication the sperm return to normal. She also says she is counseling infertile patients who may be taking a calcium channel blocker for their high blood pressure to talk to their physicians about switching to a different medication.
Current contraceptive methods for men are limited to abstinence, vasectomy, condoms, and withdrawal.