Gender Differences in the Pharmacokinetics of Oral Drugs

Establishment of rational dosage regimens requires the knowledge of pharmacokinetics and pharmacodynamics in the target population. It has been established that side effects produced by drugs are more frequent in women than in men. This may be due to two possibilities, one is that normalized dose received by women is higher than men and the other is that anatomical and physiological characteristics are a quite different. In this review, some aspects that may play a role in the generation of such differences are analyzed, including the impact on absorption, distribution, metabolism and excretion of drugs. Most of the changes can be explained by differences in volume of distribution and systemic clear- ance, however, presystemic clearance also seems to play a role in such dissimilarities. The final result, in general, is that women have higher plasma levels of drugs and usually these differences are reduced or abolished when data are normalized by the body weight, since both, volume of distribution and systemic clearance are influenced by it; however, there are some cases in which differences remain. Further research oriented to establish the role of each of the ana- tomical and physiological differences in the oral pharmacokinetics of drugs is warranted.