New hope for male birth control

Women have several choices for long-lasting, reversible contraceptives, but men who wish to control their fertility currently have limited options. They have to rely on their female partner using contraceptives, use condoms, undergo vasectomy, or abstain.

In 1960, the birth control pill was approved by the Food and Drug Administration (FDA) for contraceptive use for women. Now, 60 years later, women are still primarily responsible for pregnancy prevention using methods such as the pill, IUDs, and vaginal rings. Most options for men are either single-use, such as condoms, or difficult to reverse, like vasectomies.

Male birth control could alter sexual dynamics

Successful male birth control methods would not only increase the options for men who wish to prevent unwanted pregnancies, but also could change the dynamic between male and female sexual partners and how they share the responsibility for their reproductive health.

There are a few forms of male birth control in the clinical trial phase but male birth control methods currently in development could be pushed aside by a recent discovery.

Now, in a step toward a safe, long-lasting and reversible male contraceptive, researchers reporting in ACS’ Nano Letters have developed magnetic, biodegradable nanomaterials that reduced the likelihood of mice fathering pups for at least 30 days.

Sure, once you hear that mild testicular hyperthermia by the photothermal effect of gold nanorods could realize controllable male contraception and the physicochemical properties of iron oxide nanoparticles (IONPs), or learn that testicular injection of PEG-coated IONPs with a diameter of 50 nm (PEG@Fe3O4-50) following an alternating magnetic field (AMF) could achieve controllable male contraception, you’ll say, “Why didn’t I think of that?”

But it took a bunch of scientists to figure it out. In plain English, this means that the study offers new strategies for male contraception.

Elevated temperatures, which can be caused by wearing too-tight pants or underwear, decrease sperm count in men so researchers explored the more intense heating of nanomaterials injected into the testes as a form of male birth control.

However, the injection can be painful, the heat can damage skin, and most nanomaterials tested so far are not biodegradable.

Weihua Ding, Fei Sun and colleagues wanted to develop a safe, effective magnetic-thermal approach to male contraception that doesn’t need to be injected directly into the testes.

The researchers tested two forms of iron oxide nanoparticles, which are biodegradable and can be guided and heated with magnetic fields, as male contraceptives.

One type of nanoparticle was coated with polyethylene glycol (PEG or a polyether compound derived from petroleum) and the other with citric acid.

Although the PEG-coated nanoparticles could be heated to higher temperatures, they were not as easily manipulated by magnets as the other ones. So the researchers injected repeated doses of citric acid-coated nanoparticles into the bloodstream of mice for 2 days, guided the nanomaterials to the testes with magnets, and then applied an alternating magnetic field to the area for 15 minutes.

The nanoparticles heated the testes to a temperature of 104 F, shrinking them and inhibiting spermatogenesis before gradual recovery 30 to 60 days after treatment.

The mice couldn’t father any pups 7 days after treatment, but they were back to fathering about 12 pups per pregnant female at day 60.

The nanoparticles were non-toxic to cells and were gradually eliminated from the body, offering new possibilities for male contraception, the researchers say.

The study authors acknowledged funding from the National Key Research and Development Program of China, the Natural Science Research of Jiangsu Higher Education Institutions of China and the Open Fund of Key Laboratory of Advanced Display and System Applications of Ministry of Education (Shanghai University).

When it comes to sharing the responsibility of birth control, nearly 3 in 4 women and about 72% of men believed both sexual partners were equally responsible for using birth control.

The greater percentage of men who believed the woman should be primarily responsible for birth control, is possibly explained because this role has been taken by women for several decades.

The greatest perceived benefit of male birth control by men was increased pregnancy prevention. Over 31% of men responded they would feel more in control of their reproductive health, and an additional 34% said they would stop wearing condoms.

Over 56% of women believed male birth control would make it fair for both men and women to be responsible for birth control, while less than 38% of men agreed.

“I would be happy to have full control over my own reproduction abilities, but I would be annoyed if I had to visit a doctor’s office often to get shots or prescriptions,” said a 34-year-old male participant from Florida.

Forty-three percent of the women agreed that availability for male birth control options would allow them to feel less pressure about avoiding unwanted pregnancies, while over 27% of men would feel less pressure, too.

One study found that if 10% of men interested in male contraceptives used new contraceptive methods, unintended pregnancies would be reduced to 5.2% in the United States.

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