Women are not scaled men, clinically speaking

women are not small men, even if clinical research has treated them as such for dosing regimens
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Clinical research has fundamentally discriminated women, assuming that they are nothing more than “small” men and therefore, drugs should work mostly the same if just adjusting the dose to their lower weight.

However, this has been proven not to be the case. The physiology of the two sexes differs in several parameters, that is why women suffer 50–75% more adverse reactions from drugs than men. New research in mice offers new evidence of why not performing clinical research in females is dangerous, not only to drug research but to women.

To once and for all disentangle the relationship between body size –which was assumed to be the only parameter influencing the different effects of drugs between the sexes– and certain bodily characteristics, a recent study 1 shows the results of performing allometric analyses to 363 pre-clinical traits in male and female mice, using data from the International Mouse Phenotyping Consortium.

Among the investigated pre-clinical traits, physiological traits such as iron levels and body temperature, morphological traits such as lean or fat mass, and others such as heart rate variability showed sex differences which could not be explained by size alone. This indicates that the adjustment of drug doses to women cannot be based on a simple weight extrapolation, and that more sex-specific biomedical research is needed to provide patients with the best and most personalised care possible.

Some might doubt about the importance of including women in clinical research and might refer to economic factors to justify their exclusion. However, given the high cost for health systems associated with drug side effects and women’s high treatment discontinuation rates, investing in inclusive research might actually not only be more human but more cost-effective.


  1. Wilson, L.A.B., Zajitschek, S.R.K., Lagisz, M. et al. Sex differences in allometry for phenotypic traits in mice indicate that females are not scaled males. Nat Commun 13, 7502 (2022). doi: 10.1038/s41467-022-35266-6

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