Abstract / Summary
Background Metoclopramide is prescribed during pregnancy to treat nausea and vomiting. Despite its widespread application, there is potential for peripartum maternal metoclopramide dosing to induce extrapyramidal symptoms (EPS) in the newborn due to residual pediatric drug levels at birth. Here, a physiology-based pharmacokinetic model, including pregnancy-related changes and placental transfer values, was established and verified for metoclopramide. Human placenta cotyledon perfusion experiments were conducted to estimate placental transfer of metoclopramide. Transfer parameters were incorporated in a Simcyp PBPK model to enable predictions of fetal plasma and brain concentrations at different gestational ages (GA). Simulations were performed for the pre-cesarian section dosing of 10 milligram (mg) intravenously (IV, single dose), after which predicted fetal brain concentrations were used to calculate dopamine (D2) receptor occupancy. Findings & Conclusions Human ex vivo placental perfusion data were successfully generated and integrated into a pregnancy-specific physiology-based pharmacokinetic model to characterize maternal, fetal, and fetal brain exposure to metoclopramide. The model adequately predicted pharmacokinetics in healthy volunteers and pregnant individuals. Simulations of 10 mg IV dosing show mean metoclopramide peak concentrations of 47.0, 39.5 and 37.9 ng/mL in the fetal plasma at 24, 32 and 40 weeks GA, respectively. Residual drug levels immediately after birth were assumed to be equal to predicted fetal plasma levels. Newborn brain concentrations were predicted to be of the same order of magnitude as maternal plasma levels, with maternal plasma-to-fetal brain ratios of 1:0.98, 1:0.76 and 1:0.65 at GA 24, 32 and 40 weeks, highlighting evident distribution to the newborn central nervous system. Average newborn brain D2 receptor occupancy, which was used as a surrogate pharmacodynamic marker for EPS, remained below the 80% threshold for all simulated GAs. However, predicted population variability indicated that for a small but clinically relevant subset of newborns (~ 5% at 24 weeks and ~1% at 32 weeks GA, respectively), the 80% D2-receptor occupancy could be exceeded under standard dosing regimens, indicative of EPS risk.