Calcium Channel Blockers: Causes Male Infertility


Nifedipine, a widely prescribed hypertension drug, has been linked over the years to an increased rate of cancer, heart attack, gastrointestinal bleeding, and memory loss. Now one more adverse effect can be added to the list: male infertility. Nifedipine is a calcium channel blocker, a drug class that periodically generates controversy concerning inappropriate use.

The latest adverse effect was noted by specialists who observed that men who seek care at infertility clinics were often taking a calcium channel blocker. It was described at the annual meeting of the American Society for Reproductive Medicine and the Canadian Fertility and Andrology Society, held recently in Toronto.

Nifedipine "inhibits the trans-membrane influx of calcium ions into vascular smooth muscle and cardiac muscle," according to the Physicians' Desk Reference. Calcium channel blockers affect all areas of the body, which explains why the adverse effects are so varied. The infertility effect appears to be caused by nifedipine's ability to block calcium influx into sperm. At the Toronto meeting, Dr. Susan Benoff of NYU School of Medicine explained that these drugs alter the cholesterol content of the membrane. Sperm overloaded with cholesterol becomes nonfunctional, she explained. Because the infertility effect is reversible, some physicians suggested that nifedipine has potential as a male contraceptive.

Calcium channel blocker drugs are sold under many brand names, including Procardia, Adalat, and Cardizem. FDA approval was based on the nifedipines short-term ability to reduce blood pressure. Unlike the older drug classes for the treatment of hypertension (diuretics and beta blockers), calcium channel blockers have never been proven to reduce the rate of heart attack or stroke. Warnings are repeatedly printed in medical journals that calcium channel blockers should not be the first choice prescription to people with hypertension. Yet they are among the top-selling drugs in the country because they are heavily promoted to physicians.

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