Drug disposition during pregnancy.

This review examines the literature on drug disposition during human pregnancy. Drugs are considered on the basis of their mode of excretion and hepatic extraction ratio in order to assess the general effects of pregnancy on drug disposition. Pregnancy increases clearance of drugs whose excretion is predominantly renal and related to creatinine clearance but fails to change clearance of parenterally administered drugs that are extensively metabolized by liver and have a high hepatic extraction ratio. The data are unclear as to how pregnancy influences the disposition of drugs extensively metabolized by liver with a low to intermediate hepatic extraction ratio.