Sex, Drugs and Different Responses
Men and Women May Respond Differently to Medicines - and we need to do something about it
A 2025 study* by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) and the University of Liverpool is changing how we think about clinical trials and the future of medicine. The study confirms what many of us have long suspected: there are still important gaps in medical research, particularly when it comes to how men and women are represented in drug development.
We all know that medication goes through rigorous testing, but the truth is, many medicines have been studied mostly in men. The MHRA study found that male-only trials were almost twice as common as female-only ones.
Or if the group does happen to be mixed, they rarely include pregnant or breastfeeding women. In fact, pregnant and breastfeeding women were included in less than 2% of trials between 2019 and 2023.
This matters because men and women don’t always respond to medications the same way. Differences in hormones, metabolism and body fat (to name a few of the variables) mean that what works well or safely for one sex might not for the other**.
Moreover, women are more likely to experience side effects. Studies have shown that in more than 90% of cases, women report worse side effects, including nausea, headache, depression, cognitive impairment, seizures, and agitation. Women are also twice as likely as men to experience an adverse drug reaction.
One major factor is that women often have higher drug concentrations in their blood and take longer to eliminate drugs from their systems, yet dosing regimens have largely been based on male physiology. This one-size-fits-all approach means women are frequently overmedicated, leading to poor adherence and discontinuation of therapy.
Including women in research makes medicine better for everyone
As medical researchers, we gain valuable insights by studying how men and women respond differently to drugs, in turn allowing the creation of better and safe treatments.
Steps are already being taken to make clinical trials better. New regulations from the MHRA will aim to increase the diversity of people included in trials, including women and pregnant individuals.
What does this mean for patients?
It’s important for you to understand that all medications might work differently on different people. The more we understand those differences, the safer and more effective our treatments will become.
When being prescribed medication, feel empowered to ask your clinical practitioner for any research on interactions with different sexes.
By pushing for research that reflects everyone, not just a narrow group, we’re moving closer to a healthcare system that truly works for all.
Sources and References
* https://www.gov.uk/government/news/first-ever-mhra-analysis-of-uk-clinical-trial-applications-finds-new-opportunities-to-drive-medical-breakthroughs-for-patients
**Sex differences in pharmacokinetics predict adverse drug reactions in women Irving Zucker 1,2,✉, Brian J Prendergast 3
Photo by Tim Mossholder on Unsplash