Domperidone Use in Lactation and Risk of Severe Postpartum Mental Health Outcomes

OBJECTIVE: To evaluate whether postpartum domperidone use is associated with new-onset psychosis and other severe mental health outcomes. METHODS: We conducted a retrospective cohort study of people who filled a prescription for domperidone within 56 days of delivery between March 1, 2006, and March 1, 2022, in Ontario, Canada. Those who filled a domperidone prescription were matched 1:1 based on propensity score to an equal number of those who did not. The primary outcome was any health care contact for incident psychosis in the subsequent 365 days, with a secondary outcome of any psychiatric emergency department (ED) visit or hospitalization. Cox proportional hazards regression was used to compare outcome risk between people who initiated domperidone and those who did not. RESULTS: We identified 2,237,806 births, and 7,096 (0.3%) were followed by the individuals filling a publicly funded domperidone prescription within 56 days postpartum. After exclusions, 4,629 domperidone-exposed and 116,644 unexposed individuals remained. Overall, 4,585 domperidone-exposed individuals were propensity score matched to an equal number who were unexposed, resulting in good balance across all measured baseline characteristics. Compared with matched postpartum individuals who did not initiate domperidone, domperidone use was not associated with psychosis (6.4/1,000 person-years vs 6.4/1,000 person-years; hazard ratio [HR] 1.00, 95% CI, 0.60–1.67) in the postpartum period. We found no association between domperidone use and ED visits or hospital admissions with mental health diagnoses (38.0/1,000 person-years vs 43.4/1,000 person-years, HR 0.88, 95% CI, 0.71–1.08). CONCLUSION: Initiation of domperidone postpartum was not associated with an increased risk of new-onset psychosis or ED visits or hospital admissions with mental health diagnoses.