A version of a heart-stopping poison could be an effective form of male birth control, according to a University of Minnesota study.

Scientifically engineered ouabain — a poison traditionally used by African warriors and hunters — is nontoxic and effective at paralyzing sperm, researchers say. Experts hope this finding, plus the public’s increased interest, means scientists are one step closer to developing a reversible male contraceptive. 

Scientists have been working to create a reversible male contraceptive for decades, but the process has been difficult because male contraceptives must be risk- and side effect-free, said Rebecca Cuellar, a University research assistant professor.

Women tolerate a lot of minor side effects because of the risk of pregnancy, Cuellar said. Since men don’t worry about the physical burden of pregnancy, they don’t have to tolerate as many side effects, she said.

“I’ve made the joke before that for the last 40 years we’ve been five to 10 years away from having a male contraceptive, but we are actually really excited about the research we have going on at the University,” Cuellar said.

University researchers have engineered the molecular structure of ouabain to eliminate its cardiovascular effects, said Gunda Georg, professor and head of the University’s department of Medicinal Chemistry. The compound inhibits sperm mobility, which leaves the man temporarily infertile, she said. 

While researchers have only completed animal studies where the contraceptive was delivered in pill form, they are looking at other long-term options like implants, Georg said. 

According to a national survey co-authored by researchers at Gustavus Adolphus College, men are open to and interested in taking male contraceptives, which they see as something that can make them equal partners in preventing pregnancy, said Katie Ziemer, a research scientist who worked on the survey. 

“Men are unsatisfied with the options currently available to them, which are condoms and vasectomy,” she said. “Demand often drives science, so the more interest there is in male contraceptives, the more funding will be directed to scientific studies and clinical trials.” 

While some men worried that taking a birth control pill — often associated with female empowerment and feminism — would make them seem less masculine, the women surveyed didn’t hold this view, Ziemer said. Instead, women surveyed said they would appreciate their male partner taking the pill, and that it would increase the level of intimacy in their relationship.

While University researchers have made significant progress in developing a reversible male contraceptive, finding a pharmaceutical company to sell the drug is difficult, Georg said.

“The female pill was introduced into the market in the 1960s, and now it’s 2018 and we don’t have anything for men,” Georg said. “It’s a bit discouraging, but we’re still hopeful that with the different approaches we’re taking, we’ll eventually succeed.”