The MedMilk (Medication concentrations in human Milk) study investigates how selected medicines taken by breastfeeding women are transferred into human milk and whether this may affect the breastfed child. The study includes breastfeeding women who are already using prescription or over-the-counter medicines as part of their usual care. Participants provide samples of breast milk and urine and complete a questionnaire about maternal and infant health. The collected data will be used to quantify medicine concentrations in milk and estimate the relative infant dose. The study aims to contribute new data to support safer prescribing and more informed counselling during breastfeeding
Lactating women aged ≥18 years
Current use of one or more prescription or over-the-counter (classified within the ATC system) drugs
Able and willing to provide written informed consent
Current pregnancy during sample collection
Known and clinically significant pharmacokinetic drug-drug interactions at the time of sampling
Participants will be lactating women recruited through obstetric, neonatal, and psychiatric departments, public health visiting nurses, and counselling services across Denmark. Recruitment will be coordinated by the Department of Clinical Pharmacology, Bispebjerg and Frederiksberg Hospital, Copenhagen. The study primarily targets women using prescription and over-the-counter medicines during breastfeeding and aims to represent real-world exposure patterns across all Danish regions.
Cohort
Prospective
Prescription Drugs
DrugExposure to prescription medicines taken by breastfeeding women during routine treatment. The study does not assign medications but observes drug transfer into human milk from exposures occurring as part of usual care.
Drug concentrations in human milk
Quantification of drug concentrations in human milk, expressed in micrograms per millilitre (µg/mL). Milk samples are collected before and after the maternal dose within one dosing interval.
Relative Infant Dose (RID)
Estimation of infant drug exposure, expressed as the relative infant dose (% of maternal weight-adjusted dose).
Maternal-reported infant adverse effects
Maternal questionnaire on infant symptoms potentially related to drug exposure via breastfeeding.
Simulated infant plasma levels
We will estimate the infant plasma level of the specific drug expressed as microgram pr. millilitre μg/ml based on pharmacokinetic modelling of infant, and drug characteristics and drug concentrations in milk samples.
Simulated Area Under the Curve (AUC)
We will estimate the 95th percentile of the pediatric Area Under the Curve (AUC) (μg x h/mL) based on pharmacokinetic modelling of infant, and drug characteristics and drug concentrations in milk samples.
Biobank establishment
Milk and urine samples stored for future pharmacokinetic analyses and secondary research
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