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 The study had to be stopped due to safety concerns, however. An
independent safety board found that side effects, which included
depression and other mood disorders, outweighed the potential
benefits of the injections.
"Researchers are trying to identify a hormonal male contraceptive
that is effective, reversible, safe, acceptable, affordable, and
available," the study's technical team wrote in an email to Reuters
Health.
The researchers, led by Dr. Hermann Behre of Martin Luther
University of Halle-Wittenberg in Germany, recruited 320 healthy men
ages 18 to 45 from several countries. All had been in monogamous
relationships for at least a year with women between 18 and 38 years
old. The couples did not want to get pregnant within the next two
years.
Every eight weeks, the men received injections of long-acting
testosterone and progestin.
"Giving testosterone in high doses suppresses sperm production in
the male reproductive organ or the testes over several weeks,"
according to the researchers.
Adding another hormone, "usually a progestin, helps increase the
suppression of sperm production to lower levels, in more numbers of
men," they continued. "It will also help to sustain it, so that
injections may be given less frequently."
In 274 men, or 86 percent, sperm counts dropped to the target of
less than 1 million per milliliter of semen after 24 weeks. Normal
sperm counts range from 40 to 300 million per milliliter, according
to the National Infertility Association.
Four pregnancies occurred among 266 couples over 56 weeks of follow
up, the researchers report in the Journal of Clinical Endocrinology
and Metabolism.
The failure rate of this form of birth control was 7.5 percent, they
found. The U.S. Centers for Disease Control and Prevention says male
condoms have a failure rate of 12 percent. In women, birth control
pills, patches and rings have a failure rate of about 9 percent.
Failure rates are below 1 percent for female implants and
intrauterine devices and sterilization surgeries in both men and
women.
Nearly 1,500 adverse events were reported during the study. About 39
percent were not related to the injections, however.
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Of the side events thought to be related to the injections, about 46
percent of men reported acne, about 23 percent reported injection
site pain, about 38 percent reported an increase in libido and
several reported mood disorders, including emotional disorders,
hostility, depression and aggression.
In addition to safety concerns, there are other unknowns about this
approach to birth control, said Dr. Landon Trost, who is head of
andrology and male infertility at the Mayo Clinic in Rochester,
Minnesota. For example, in most participants, sperm production
rebounded after the injections stopped - but the study only include
men with health sperm counts.
"What we don’t know is how it affects men without healthy sperm
counts," said Trost, who wasn't involved with the new study.
It's important to realize, he added, that this form of birth control
- unlike condoms - would not protect against sexually transmitted
infections or disease.
"The question is what is the real practical role for this," Trost
said. There may be some use for this approach among men and women in
committed relationship, he added.
The World Health Organization, whose researchers are were among
those who worked on the new study, currently recommends condoms and
sterilization as the only forms of male birth control.
SOURCE: http://bit.ly/2ePgL0u Journal of Clinical Endocrinology and
Metabolism, online October 27, 2016.
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