Investigating the Transfer of Lisinopril into Human Milk: A Quantitative Analysis.

Lisinopril is commonly prescribed to manage conditions such as hypertension and heart failure. While concerns about fetal toxicity have traditionally limited the use of lisinopril in women of reproductive age, recent ACOG guidelines promote aggressive treatment of hypertension, which may require the use of pharmacologic agents not previously considered in the postpartum period. We aimed to estimate infant exposure to maternal lisinopril via breastmilk and report the tolerance of the breastfed infant. Five volunteers taking lisinopril provided samples of their human milk and their associated health information for research through the InfantRisk Center Human Milk Biorepository. The milk pharmacokinetics of lisinopril were measured using liquid chromatography-mass spectrometry. The mean milk concentration of lisinopril was 0.49 ng/mL per 10 mg daily dose. The Relative Infant Dose (RID) was 0.06% for lisinopril, more than 100 times lower than the standard 10% safety threshold. The minimal transfer of lisinopril into human milk in this study suggests the drug is unlikely to pose a clinically significant risk to healthy breastfed infants.