New research reports on a drug dose gender gap. Clinical trials historically have more men than women, and now women are experiencing side effects from being prescribed doses that aren’t fit for them.

The research, a joint effort from University of California, Berkeley, and the University of Chicago, was released in the journal Biology of Sex Differences.

The study found 86 drugs approved by the Federal Drug Administration (FDA) with clear evidence of a gender gap. In other words, many adverse drug reactions could be predicted by sex differences.

Their results point towards a dangerous bias in the pharmaceutical industry that is harming women worldwide.

A short history of the drug dose gender gap

The unscientific claim that female hormone fluctuations make women too tricky to study persisted in medical trials until very recently. Women were historically absent from clinical trials because of this claim.

Due to liability concerns, women of childbearing age were often excluded altogether from drug testing, which led to tragic cases. The highest profile incident happened in the 1950s and early 1960s and concerned the drug thalidomide, which caused thousands of serious birth defects in children globally.

Thirty years on from the thalidomide disaster, in the 1990s, women of childbearing age finally started to be included in drug trials. But it wasn’t until 2016 that recruiting both men and women became mandatory for receiving grant funds in the US.

Even since this change, only 26% of trials have made an explicit comparison between the varying impacts of tested drugs on male and female participants.

This new research highlights that a drug dose gender gap in the response to medication exists, and that the one-size-fits-all approach mistreats women.

medication capsules on wooden surface and spoon
Medication capsules on wooden surface and spoon. Photo credit: Michael Longmire, Unsplash.

Double the adverse drug reactions

The research collated data from thousands of medical journal articles. Antidepressants, painkillers, and many other well-known medications were among the 86 drugs presenting clear evidence of sex differences.

Women experience the more severe side effects in 90% of cases. A full range of reactions was taken into account, from headaches and nausea, to seizures, hallucinations, and depression. Collectively, women were almost twice as likely as men to encounter adverse drug reactions.

Some awareness of this is already present in the medical community. For example, with Ambien, a popular sleep medication. The drug in Ambien, zolpidem, is known to last in the bloodstream of women for a longer period than in men. As of 2013, the FDA halved the recommended prescribed dosage for women.

The overarching issue is made clear by the case of Ambien. Action wasn’t taken until many women reported significant mental impairment and drowsiness the following morning, and even increased frequency of car accidents.

assorted-shape medication pill lot
Assorted-shape medication pill lot. Photo credit: Stephen Foster, Unsplash.

A custom-fit future

Researchers from this latest study are now calling for the overmedication of women to be addressed at the clinical trial phase.

Simply studying male and female participants isn’t sufficient. According to the report, trials should also be required to develop “rational, feasible sex-based dosing adjustments.” Further recommendations include sex-adjusted dosing guidance being disseminated to doctors and appearing on all drug labels.

Such considerations are widely absent at the moment. Until action is taken to change this, the gender gap in healthcare persists.

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