For obvious reasons, almost none of the research projects involved in understanding pregnancy-induced changes in drug disposition has been conducted in women with cancer or in other women receiving cancer chemotherapy for adverse indications.

This chapter, therefore, will overview general principles governing changes in drug disposition during pregnancy, assuming that these mechanisms will be operative for cancer drugs too.

Clinical case

One of your patients, a G1 P0 epileptic woman (65 kg in late gestation) who was maintained on 400 mg/d of phenytoin taken in two equal doses every 12 hours has just had her first and only grand mal seizure during pregnancy at 26 weeks of gestation. Upon arrival to the emergency room her phenytoin level was 5 mg/L 10 hours after her evening dose. Three through levels taken before, at various times during pregnancy, were between 12 and 17 mg/L. What are your thoughts about the mechanism leading to this seizure?

Introduction

While the potential hazards to the unborn baby from medications administered to the pregnant woman are a major concern, one should be very careful not to neglect the maternal part of the fetomaternal unit. It has been universally agreed that the well-being of the mother should dictate her need for drug therapy and that one should not subject pregnant women to suboptimal therapy that may endanger them.