Why is it so hard to make a hormonal birth control pill for men?

Multiple hormonal birth control methods for men are in the works, but there are also several obstacles. (Photo: Getty Images)
Multiple hormonal birth control methods for men are in the works, but there are also several obstacles. (Photo: Getty Images)

Like the Loch Ness monster, the male birth control pill seems to be one of those rumors that rears its head every once in a while and then vanishes into the ether.

After years of hearing that new forms of male birth control are on the horizon — beyond the current options of abstinence, vasectomy, condoms, and the less-than-reliable withdrawal method — not to mention the fact that women have had the Pill for nearly 60 years, it’s hard not to wonder, what’s taking so long? Why is it so challenging to bring a safe and reversible method for men to market?

Part of it comes down to anatomy. Women typically release one egg per month. Now compare that with the constant cascade of sperm. According to New York University’s ScienceLine.com: “A healthy adult male can release between 40 million and 1.2 billion sperm cells in a single ejaculation.”

As Michael Eisenberg, MD, director of male reproductive medicine and surgery at Stanford Health Care, in California, puts it: “It’s a very hearty, robust, and redundant system.”

Adds Brian Nguyen, MD, assistant professor of clinical obstetrics and gynecology at the Keck School of Medicine at the University of Southern California: “What’s inherently more difficult for the male method [of birth control], you have to stop a process that is otherwise continuous, whereas with the female method, if you’re able to stop ovulation alone that would suffice.”

That said, Nguyen points out it’s easier to confirm that male contraception is working. “All I need to do was ask for a semen sample and see whether he has no sperm or they’re not functional, not swimming,” he tells Yahoo Lifestyle. “Whereas for women, there’s nothing noninvasive that would tell you.”

How male birth control methods work

While there are different roads to get there, the end goal is to block the avalanche of sperm from getting to the egg and prevent fertilization. “You can immobilize the sperm — you can actually create a physical barrier that prevents sperm from getting to an egg — or you can stop creating sperm,” Nguyen explains. “Our job is to think of ways to do it from a pharmacologic or device standpoint.”

As far as physical barrier methods, one potential reversible and nonhormonal procedure (Vasalgel) involves placing an occlusive gel in the vas deferens — the duct that shuttles sperm away from the testicles toward the penis. The gel blocks sperm from getting through, but likely not seminal fluid, so men can still ejaculate without causing a pregnancy.

There are also hormonal injectables and pills that target sperm production, either by stopping sperm from being produced or preventing them from maturing so they can’t fertilize an egg, Eisenberg explains.

One promising daily pill, called dimethandrolone undecanoate (or DMAU), effectively lowered testosterone and other hormone levels to stop sperm production and was well tolerated (in other words, no serious side effects), according to a 2018 study in Male Reproductive Endocrinology. Researchers are looking into longer-term studies of the drug.

There’s also a hormonal topical gel in the works, which Nguyen says is the method he and his colleagues are “most excited” about. The gel, which is applied daily to arms and shoulders, contains testosterone and nestorone (a synthetic form of progesterone). “It halts sperm production,” he says, noting it’s in human trials right now, including in three cities across the United States.

Eisenberg says that hormonal methods tend to receive the most attention and are further along than other methods. “And the reason being we’ve had so much experience with women’s contraception for so long, looking at the safety profiles,” he says. “And some of the drugs are not that different from what we’d use for women.”

However, one roadblock is that it’s harder to bring new birth control methods to market than before — though that is ostensibly for a good (safety related) reason. “The demand for the current standards is much higher than it was before,” Nguyen says. “The same barriers to entry we face now were not in place back then. The pressure is so high that any possible adverse event, [researchers] are extremely careful — and that level of care requires a significant amount more funding and manpower.”

Case in point about the pressure to avoid side effects with new methods: A clinical trial of an injectable contraceptive for men administered every eight weeks, which looked promising — the 2016 preliminary results found it was nearly 96 percent effective at stopping sperm — was shut down by a safety panel. The panel stated that “the risks to the study participants outweighed the potential benefits to the study participants,” citing its concerns about reported side effects — namely, mood changes, depression, pain at the injection site, and increased (yes, increased) libido.

Like any hormonal birth control method, there will be potential side effects, including mood changes — though, surprisingly, it’s not always down and instead it can boost mood — libido changes, weight gain, and acne. However, Nguyen says in general, these would be very mild depending on the formulation.

Other roadblocks to male birth control

Male hormonal birth control could have a significant effect on unintended pregnancies — which make up nearly half of all pregnancies in the U.S. each year, according to the Guttmacher Institute. “In theory, it should drop it,” says Eisenberg. “It’s certainly an untapped market. It’s a public health issue — unwanted pregnancies are certainly a huge deal for a society, economically and socially.”

Nguyen notes that hormonal methods are the closest to market. But based on the small number of researchers, funding, and pharmaceutical companies actively pursuing new male birth control methods, he estimates that the first one will probably hit the market around 2030.

That could possibly be sped up if more men stepped up and asked for it. “Male contraception isn’t really going to happen until more men realize their responsibility and demand it to be addressed,” Nguyen says. “And to have their concerns validated by physicians and scientists.”

Nguyen knows that male contraceptives have inherent challenges that go beyond efficacy and side effects, including changing some men’s perceptions about how active a role they can play in helping to avoid an unintended pregnancy. “Do I think that the majority of guys are going to be super excited about using this drug compared to similar drugs for women? Probably not,” he says. “But it opens a conversation about what is the responsibility of male partners when it comes to pregnancy prevention. And it’s no longer going to be a situation of, ‘I don’t have to do anything.’”

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