Pharmacokinetics in pregnancy; clinical significance.

In pharmacokinetics drug absorption, distribution, clearance, and bioequivalence are usually considered, but during pregnancy the most important variable is adherence or compliance. Pharmacokinetic changes during pregnancy that may lead to changes in maternal drug use are described through presentation of cases highlighting the relevance of these changes. Non-invasive methods of pharmacokinetic analysis, such as determining concentrations of drug in hair, are now being tested and used.Pharmacokinetics are important, but one needs to consider the entire pregnant state and its circumstances when treating women. One treats people, not a "volume of distribution" or a drug level. Therapy should be individualized as much as possible, addressing kinetic changes in the context of dynamic alterations and the effects of underlying medical conditions. To ensure that women are not orphaned from advances in drug therapy, much more research is needed into the determinants of pharmacokinetic and pharmacodynamic changes in pregnancy.