A study on a new hormonal birth control shot for men found it to be effective in preventing pregnancy, but the study was cut short after hundreds of complaints about negative side effects.
The study involved 320 healthy men who ranged in age from 18 to 45.
The men were given an injection of a synthetic form of testosterone and a synthetic derivative of progesterone and estrogen every eight weeks, which reduced their their sperm count to 1 million per milliliter or less.
Researchers found it was effective in nearly 96 percent of continuing users.
Enrollment began in 2008 and the trial was supposed to continue through 2012, but ended in 2011.
Participants reported 1,491 adverse effects, including acne, muscle pain, increased sex drive and depression.
According to CNN, about 3 percent of the men reported feeling depressed. Recent studies on women have linked the use of hormonal birth control with an increased risk of depression.
Twenty men dropped out of the study early because of side effects. But researchers said 39 percent of the side effects reported were not related to the shots.
Despite the side effects, more than 75 percent of participants said they were willing to continue with the shots.
After stopping the shots, it took most men 12 to 26 weeks for sperm counts to recover to levels described as “fertile” by the World Health Organization.
The study was co-sponsored by the United Nations and published in the Journal of Clinical Endocrinology and Metabolism.