Study Finds Lack of Women in Clinical Trials Leads to Incorrect Drug Dosing

Medications are intended to help, but women may be experiencing ill-effects from many of them because of gender imbalances during the testing process, according to a new study. Researchers found that drug dosages have typically been set using data collected from clinical trials conducted primarily on men, leaving many women overmedicated or dealing with side-effects.

The study, from researchers at the University of California, Berkeley and the University of Chicago, was published in the journal Biology of Sex Differences. During their work researchers analyzed data from over 5,000 medical journal articles to evaluate the sex breakdown of study participants. They noted that common practice in trials is to prescribe equal drug doses to men and women despite differences in size, body weight and biologic processes. That has generally led to higher blood concentrations and longer elimination times of medications for women.

In total the team found data on 86 medications approved by the Federal Drug Administration (FDA) including antidepressants, cardiovascular, anti-seizure and analgesic medications. “When it comes to prescribing drugs, a one-size-fits-all approach, based on male-dominated clinical trials, is not working, and women are getting the short end of the stick,” said lead study author Irving Zucker, professor emeritus of psychology and integrative biology at UC Berkeley.

Researchers found that in more than 90% of cases women experience adverse drug reactions like nausea, headache, depression, drowsiness, cognitive deficits, excessive weight gain, seizures, hallucinations, agitation, and cardiac anomalies. They experienced side effects at nearly twice the rate of men.

The FDA seemed to acknowledge the value of individualized dosing based on sex in 2014 when it recommended it for the drug zolpidem, commonly known as Ambien. It was found that the same dose in women that was recommended for men caused two times the drug level in the body due to differences in metabolism, according to a study published in Pharmacy Practice. The result was morning-after drowsiness, which could cause dangerous driving conditions, so the FDA revised their guidelines to recommend sex-specific dosing.

It wasn’t too long ago that women were left out of the drug testing process altogether. Citing concerns over risks to their childbearing potential, researchers excluded women from drug trials and focused solely on men until as recently as 1993. That’s when the National Institute of Health (NIH) started requiring the inclusion of women in any federally supported phase III clinical trial. But in 2018 a review of NIH-funded trials found that still only 26% of trials were reporting any outcome data broken down by sex.

Zucker and his co-researcher, Brian Prendergast, made several recommendations in their study to help women and medical professionals when it comes to prescribing medications. These included system-wide changes like establishing sex parity in the drug testing and approval process of the Department of Health and Human Services, and industry-level reform including instruction in sex-differences in drug treatment for doctors.

Whether these changes take effect anytime soon remains to be seen. But this is a conversation every woman can have with her doctor today and perhaps take even better care of her own health.