Contraceptive for Men, Similar to Pill, Gets 1st U.S. Test
For the first time in the United States, researchers are testing a male contraceptive that works like the female birth control pill to determine whether it is effective in preventing pregnancy.
In a trial that began in April, 1987, researchers at the University of Washington have been studying about four dozen couples in the Seattle area as part of a global research project sponsored in part by the World Health Organization.
The goal is to find out whether men who receive weekly injections of testosterone enanthate, a synthetic hormone, become infertile.
If the research is successful, scientists believe that the drug could be the forerunner of the first male contraceptive to be introduced since the centuries-old condom.
The “exceedingly important study” likely will serve as the first step in trying to develop a new “male method” of contraception, said Gabriel Bialy, chief of the contraceptive development branch of the National Institute of Child Health and Human Development, part of the federal government’s National Institutes of Health.
Researchers have known since the late 1940s that regular injections of synthetic hormones can cause a reversible condition in which males produce little or no sperm, as measured by laboratory analysis instead of pregnancy rates. But until the current tests, no formal studies had been conducted to prove that the drugs work as contraceptives.
“There have been several clinical trials testing various hormones on men, but each time couples on these programs were advised to use other forms of contraception,” Dr. C. Alvin Paulsen, the study’s lead researcher and a professor of medicine and endocrinology at the University of Washington, said in an interview Wednesday.
Paulsen said that the project’s goal is to find a “safe, reversible and reasonably effective” method of male birth control. He defined reasonably effective as a method that would approach the failure rate of condoms, which he estimated at 5% to 17%.
In results reported so far, he said, there were no pregnancies among 11 couples who spent one year using only the drug as a contraceptive. Paulsen said that the tests should be concluded by the end of 1991.
Testosterone enanthate works by temporarily shutting off hormones that are produced by the pituitary gland and are necessary for sperm production. Men who participate in the study are given weekly injections of 200 milligrams of the drug over a period of several months to induce azoospermia, or zero sperm production. In the tests, azoospermia is determined by laboratory analysis of three consecutive samples, one taken every two weeks.
Since “that is a small point in time and sexual activity is usually more frequent,” Paulsen said, it remains uncertain whether a lab diagnosis of azoospermia will result in a low or zero pregnancy rate in normal couples who are relying only on the injections.
During the early months of the injections, study participants and their partners continue to use some form of barrier contraception, either condoms or a diaphragm, Paulsen said.
After the men reach zero sperm production, which occurs more rapidly in some men than in others, they and their partners abandon other means of contraception and rely only on the injections for a period of one year. At the end of that year, the drug is withdrawn and the men are studied to see how quickly they “recover” their sperm count, Paulsen said.
Some men never reach zero sperm count, he said. But many develop a low sperm count, or oligospermia, as a result of the injections. In another phase of the trial, men with low sperm counts induced by the drug will be studied to determine pregnancy rates.
“We need to define that level of sperm production that will still be associated with effective contraception for men who do not become azoospermic,” Paulsen said. “Our expectation is that if members of this group stay at very low levels for a year, they won’t experience a failure rate that exceeds conservative estimates of the condom failure rate.”
Short-term side effects of the drug include slight weight gain--an average of six pounds--and acne--generally among those patients who had experienced acne during puberty, Paulsen said.
The drug’s biggest drawback, however, is that weekly injections are required, he said. Many researchers doubt that such a regimen would be popularly accepted.
At this point, Paulsen noted, “we are studying a concept rather than a product.”
Nevertheless, he said, researchers are expected to try to develop alternative delivery systems, such as biodegradable hormone pellets that could be placed under the skin and would last for several months or other hormones “that last longer in the body.”
Paulsen said that a new male contraceptive could be a welcome alternative to surgical sterilization--tubal ligation or vasectomy--both of which usually are permanent. It also would provide an option for couples in which the woman has used birth control pills for long periods of time.
One of testosterone enanthate’s big advantages, Paulsen said, is that its effects are quickly reversed once the injections are stopped.
In fact, the drug has been used since about 1950 to treat infertility in men. In patients with a low sperm count, supplemental dosages of testosterone are given to stop sperm production, and when the drug is withdrawn, sperm production often is stronger.
The University of Washington is one of nine institutions, and the only one in this country, testing an injectable male contraceptive. Besides the World Health Organization, the State Department’s Contraception Research and Development Program in Norfolk, Va., is funding the work.
BACKGROUND
No effective male contraceptive has been developed since the condom, believed to have been introduced two centuries ago. So far, the only alternative for men has been vasectomy, a surgical sterilization procedure that generally is permanent. Oral contraceptives for women were first marketed in 1960 and have become the most widely used form of contraception in almost every country.
