Medication Use During Breastfeeding—An Understudied Population: A Five‐Year Experience in the Pharmacovigilance Center of Lyon

Medication use during breastfeeding is common, yet data on drug transfer into breast milk and infant exposure remain limited. This study describes real-world requests concerning medication compatibility with breastfeeding managed by the Lyon pharmacovigilance center over five years. We conducted a descriptive observational study including all requests recorded between January 2019 and December 2023. Characteristics of infants, medications involved, and recommendations provided were analyzed. A total of 2,473 requests were included, corresponding to approximately 500 per year. Most requests originated from patients (44%), allied health professionals (29%), or specialists (25%), with two thirds occurring postpartum. Overall, our recommendations supported breastfeeding in 87% of cases, either unconditionally or under specific conditions, such as clinical monitoring, therapeutic adjustments, or timing strategies. Only 13% of cases resulted in an unfavorable recommendation, for either treatment or breastfeeding discontinuation, due to formal contraindications, insufficient therapeutic benefit, or limited safety data. Polytherapy was observed in 35% of cases and was associated with more restrictive recommendations. Medications used for chronic conditions accounted for 36% of cases such as antihypertensives, antiepileptics, or psychotropic agents. Treatments for acute conditions included anti-infectives, analgesics, contrast agents, or anesthetics. Reported adverse effects in infants were rare and non-serious. In most cases, a recommendation supporting breastfeeding during maternal treatment, with or without conditions, was provided. However, uncertainty persists, particularly in complex or poorly documented situations. This work highlights the need for reliable, accessible information, inclusion of breastfeeding women in clinical research, and strengthened regulatory and postmarketing evaluation strategies to ensure infant safety health.