Peer-reviewed article
Clozapine placental passage at delivery: an update
Imaz M, Lera S, Roda E, Roca A, Torres A et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This is a clinical pharmacology study examining how clozapine (an antipsychotic medication) passes from pregnant mothers to newborns at delivery. Researchers measured drug levels in six mother-infant pairs and found partial placental passage of the drug. The study reports low rates of neonatal complications but is too small to draw firm conclusions about medication safety in pregnancy.
Key points
- Mean infant-to-mother ratio for clozapine was 0.44 and for norclozapine was 0.28, indicating partial placental passage
- Only 16% neonatal complication rate observed (1 out of 6 cases)
- Weak correlation found between maternal and cord blood drug concentrations
- Study limited by small sample size (six pregnancies) and mixed medication exposure (5 polytherapy cases)
Limitations
This is a very small retrospective case series (n=6) with no comparison group, so it cannot establish causality or generalizable safety conclusions. The study acknowledges limited statistical power to examine associations between neonatal drug levels and outcomes.
Abstract
Introduction Clozapine is an effective second-generation antipsychotic that is approved for treatment-resistant schizophrenia and risk reduction of recurrent suicidal behavior in schizophrenia or schizoaffective disorder. Its available pregnancy pharmacikinetics data remain limited, which presents a challenge for clinicians managing women taking clozapine during perinatal period . Objectives The aim of this study was to provide new data of clozapine and norclozapine placental passage and neonatal outcomes. Methods We retrospectively studied a consecutive case series of six pregnancies where there was clozapine exposure (5 in politherapy and 1 in monotherapy). Clozapine and norclozapine serum concentrations were determined in the mother-infant pairs on the day of delivery (intrapartum maternal blood and umbilical cord blood respectively) and measured using a validated high-performance liquid chromatography method. The within- and between-day precision expressed as the coefficient of variation (CV)% were both <10%. The limit of quantification (LoQ) was 5 ng/mL. Neonatal outcomes were reviewed from pediatric records. Results The mean infant-mother clozapine and norclozapine ratio at delivery were 0.44 (SD=0.13) and 0.28 (SD=0.05) respectively. There was a weak positive correlation between maternal and umbilical cord clozapine and norclozapine serum concentratios (Pearson correlation coefficient 0.183, p=0.769 and 0.827, p=0.084 respectively). The rate of neonatal complications was 16%. One neonate (16%) , whose mother had drug abuse history during pregnancy, presented with a generalized neurodevelopment delay and the consequent need for continuous intensive care. Conclusions In our study, placental passage of clozapine and norclozapine was partial during delivery. Statistical power was limited for examining te association between neonatal clozapine levels and neonatal outcomes. Disclosure No significant relationships.