PHILADELPHIA (CBS) — A once-a-day contraceptive pill for men is a step closer to approval after early tests show it to be both safe and effective, according to researchers.

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In a study, the oral birth control pill called dimethandrolone undecanoate (DMAU) was taken once a day, according to the study’s senior investigator, Dr. Stephanie Page, professor of medicine at the University of Washington in Seattle, Washington.

“DMAU is a major step forward in the development of a once-daily ‘male pill,’” Page said. “Many men say they would prefer a daily pill as a reversible contraceptive, rather than long-acting injections or topical gels, which are also in development.”

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The study included dozens of men between 18 and 50 years of age, separated into groups, as some received an inactive placebo and others received DMAU.

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At the highest dose of DMAU tested, 400 mg, the men reportedly showed “marked suppression” of levels of their testosterone and two hormones required for sperm production.

Page noted they are consistent with effective male contraception shown in longer-term studies.

“Despite having low levels of circulating testosterone, very few subjects reported symptoms consistent with testosterone deficiency or excess,” Page said.

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More long term studies are in the works to confirm that DMAU taken every day blocks sperm production.