RÉSUMÉ
Postpartum depression occurs in 14.5% of women in the first 3 months after birth. This study was an 8-week acute phase randomized trial with 3 cells (transdermal estradiol [E2], sertraline [SERT], and placebo [PL]) for the treatment of postpartum major depressive disorder. However, the study was stopped after batch analysis revealed that the E2 serum concentrations were lower than prestudy projections. This paper explores our experiences that will inform future investigations of therapeutic E2 use. Explanations for the low E2 concentrations were as follows: (1) study patch nonadhesion, which did not explain the low concentrations across the entire sample. (2) Ineffective transdermal patch preparations, although 2 different patch preparations were used and no significant main effect of patch type on E2 concentrations was found. (3) Obesity, at study entry, E2-treated women had body mass index of 32.9 (7.4) (mean [SD]). No pharmacokinetic data comparing E2 concentrations from transdermal patches in obese women versus normal weight controls are available. (4) Induction of cytochrome P450 (CYP450) 3A4 and other E2 elimination pathways in pregnancy. CYP4503A4 is induced in pregnancy and is a pathway for the metabolism of E2. Conversion to estrone and phase II metabolism via glucuronidation and sulfation, which also increase in pregnancy, are routes of E2 elimination. The time required for these pathways to normalize after delivery has not been elucidated. The observation that transdermal E2 doses greater than 100 µg/d did not increase serum concentrations was unexpected. Another hypothesis consistent with this observation is suppression of endogenous E2 secretion with increasing exogenous E2 dosing.