P.II.B.4.1. Pharmacokinetic studies on pregnancy-related physiological changes
If use of a medicine during pregnancy is indicated and from all available evidence, there is no suggestion of harm, it may be appropriate to evaluate the impact of pregnancy on medicine plasma levels in pharmacokinetic (PK) studies; sometimes, it is suggested that free rather than total medicine plasma levels are monitored in pregnant women. Such studies aim to inform on dose adjustments arising from changes in plasma levels affected by pregnancy related physiological changes. Examples include some anti-human immunodeficiency virus (HIV) products, where under-treatment may result in enhanced vertical viral transmission; diabetes or asthma treatment, where good disease control in the mother enhances the likelihood of a healthy child; or products with a relatively narrow therapeutic window, where higher plasma levels may increase the risks of adverse reactions in the mother and lower plasma levels may diminish efficacy.