TORONTO, Sep 29 (Reuters Health) -- Calcium channel blockers, used to treat high blood pressure, may be linked to male infertility. This observation suggests that drugs that block calcium entry into sperm may also work as a male "Pill," researchers reported at the joint annual meeting of the American Society for Reproductive Medicine and the Canadian Fertility and Andrology Society.
Dr. Susan Benoff, associate professor of OB/GYN and cell biology at the New York University School of Medicine and colleagues from the University of Rochester Medical Center, Rochester, New York, presented study results that indicate the calcium channel blocker nifedipine causes reversible male infertility.
At a press briefing on Tuesday, Benoff noted that their research stemmed from earlier observations that men who presented to their infertility clinic were often taking a calcium channel blocker.
"We would not have guessed this if we had just looked at patient semen analysis (in that the semen) were perfectly normal, but yet they were giving us fertilization failure," said Benoff. Once patients were switched to alternate medications that did not block calcium influx into sperm, "we were able to restore fertility in these men and they were able to initiate a pregnancy either by coitus or other means," she added.
Having definitively proved that calcium channel blockers could lead to reversible male infertility, the team subsequently determined that these drugs act by changing the cholesterol content of the membrane. "If you load sperm with cholesterol, you can make them non-functional and that is what these drugs are doing," said Benoff.
The researcher also noted that regulating sperm through cholesterol metabolism is not an idea that has been previously pursued, "even though we know that sperm have to lose cholesterol in order for them to be able to bind to the zona pellucida," an outer layer of the egg. If sperm are unable to bind to the zona pellucida, they are unable to fertilize the egg.
Drugs that specifically trigger sperm to synthesize more cholesterol could be specifically developed as a male contraceptive, the investigators conclude.
The team is currently having difficulty securing funding for their work, partially because industry is concerned that people who require antihypertensive therapy may not wish to take medications that cause infertility.
Benoff advised physicians that if they have a male patient on a calcium channel blocker and the patient appears to be infertile, it is reasonable to try alternative blood pressure medication. Men should then wait approximately 3 months before attempting to impregnate their partner in order for new sperm to generate which have been unaffected by the calcium channel blocker.
