27 August 2015updated 04 Oct 2023 10:23am

The alcohol safety of new “female Viagra” drug was tested mostly on men

An investigation into the libido-enhancing drug’s side effects was carried out on a group of 23 men and two women. Spot the problem?

By Barbara Speed

Say you’ve designed a new libido-boosting drug aimed specifically at women, which, as it turns out, reacts badly with alcohol. You need to carry out further testing to investigate the side effects. Do you:

A) run a study with a group of mostly male subjects?

B) run a study with a group of mostly female subjects?

To even the average layperson, the answer seems obvious. But drug company Sprout Pharmaceuticals, creator of new headline-grabbing “female viagra” drug Addyi, decided in its infinite wisdom to go ahead with option A anyway.

Addyi, is according to Sprout, to be used “for the treament of premenopausal woman with acquired generalised hypoactive sexual desire disorder”, yet in research designed to investigate the interactions of the drug with alcohol, the company used a study group of 23 men and only two women.

Let’s look the study itself. In the notes on the trial supplied by the FDA, it’s described thus:

“A dedicated alcohol interaction study with Addyi in 23 men and 2 premenopausal women.”

OK, perhaps, for some reason, the researchers wanted to study two women’s reaction, with a control group of, er, 23 men. Let’s give them the benefit of the doubt, and read on.

The study summary then notes that “four of 23 subjects” who were given the drug plus two glasses of wine displayed hypotension (low blood pressure) or syncope (loss of consciosuness caused by hypotension). “Six of the 24 subjects” given four glasses of wine plus the drug experienced these side effects.

The problem here is that neither of these conclusions separates the results for gender – it could be that both women fainted after a few glasses of wine, or neither did. This implies that the researchers weren’t particularly interested in exploring any gender difference in results, depite the fact that, as DrinkAware notes, men and women metabolise alcohol differently. Presumably, they metabolise a drug aimed at the female libido differently, too.

In Sprout’s defence, the skewed study, first picked up by New York Magazine‘s Science of Us vertical, was not one of the original clinical trials carried out on Addyi. Instead, it was a Risk Evaluation and Mitigation Strategy (REMS). The FDA, which approves new drugs, can require manufacturers to carry out these REMS studies either before or after a product goes on the market to further understand known side effects.

This REMS was carried out after 13 of clinical trials on the drug, all of which used test groups of women. This sceenshot from the drug’s safety information page gives you an idea:

Screenshot from Addyi’s listing on a pharmacy intelligence site.

So we’re not implying that the drug wasn’t rigorously tested – in fact, it was rejected twice by the FDA before it was finally approved. But the REMS study is still significant: the drug’s manufacturers recommend that users shouldn’t drink alcohol at all during treatment, thanks to the fainting and blood pressure side effects (which actually contributed to the FDA’s earlier decisions to reject the drug). This further investigation, and the patient advice it fed into, is pretty useless to female users if it was carried out mostly on men.

I asked Sprout Pharmaceuticals why the study had such an unhelpful gender divide, and a spokesperson told me:

The alcohol interaction study, which was designed with FDA guidance, required participants to drink the alcoholic equivalent of a half a bottle of wine within 10 minutes on a nearly empty stomach before taking Addyi. More men than women agreed to enroll in this kind of study… Sprout plans to conduct post-marketing studies to further evaluate the effects of alcohol in women when taken with Addyi.

The answer: they just didn’t get enough women signing up. It seems reasonable to expect a bit more of drug companies, especially following a series of articles in Nature journal in 2010 outlining how an over-reliance on men in drug trials, along with other gender inequalities in biochemsitry, are “undermining patient care”. Let’s hope the “post-marketing studies” on Addyi actually focus on the drug’s target audience.