Subjects took the drug or placebo for 28 days, once daily with food (DMAU must be taken with food to be effective).
At the highest dose of DMAU tested, 400mg, subjects showed "marked suppression" of testosterone levels and two other hormones necessary for sperm production.
"Longer term studies are currently under way to confirm that DMAU taken every day blocks sperm production."
All groups taking DMAU did have weight gain and decreases in HDL ("good") cholesterol.
DMAU, which is being developed by the National Institutes of Health, Eunice Kennedy Shriver National Institute of Child Health and Human Development, contains undecanoate, a long-chain fatty acid which the researchers believe slows this clearance.
The trial investigated three different doses of DMAU (100, 200 and 400mg), as well as two different formulations inside the capsules (castor oil and powder).
The dose groups included five subjects randomly receiving an inactive placebo, while another 12 to 15 men received DMAU. Participants took the drug or placebo for 28 days, once daily, with food.
The results revealed that, at the highest dose of DMAU (400mg), participants showed "marked suppression" of levels of their testosterone and two hormones required for sperm production.
Arthi Thirumalai, M.B.B.S., from the University of Washington Medical Center in Seattle, and colleagues examined the safety, tolerability, pharmacokinetics, and pharmacodynamics of 28 days of daily dosed oral DMAU
in healthy men aged 18 to 50 years.