Effect of sex on the distribution of anticholinergic medications
In general, males are larger than females across the lifespan, with increased height, body mass index and waist circumference. Comparatively, women have increased adiposity45. This difference in body composition has failed to show much difference in actual drug distribution and any differences attributable to this can largely be explained by differences in total body mass46. Distribution of drugs to the brain is dependent upon the lipophilic nature of the blood-brain barrier which favours passage and accumulation of lipophilic drugs. At this time, no statistically significant difference has been found between similarly aged women and men with respect to albumin permeability of the blood brain barrier47 which likely can be extrapolated to at least some medications. The brain is also protected by p-glycoprotein, which prevents drugs from accumulating in the brain by pumping them from brain capillary endothelial cells to the blood48. These mechanisms have not demonstrated any sex difference.