The ACE-inhibitors is one group of essential medication for which reliable data on the safety during breastfeeding is lacking. ACE inhibitors are indicated for several severe or life-threatening disorders like hypertension, heart failure or nephrotic range proteinuria and diabetic nephropathy. However, data on the transfer of ACE inhibitors into the human breast milk remains very limited. After delivery, ACE inhibitor therapy is often postponed if the mother is breastfeeding, requiring multiple other medications to control the disease, or switched from long to short acting forms, decreasing therapeutic adherence. Limited available data shows that the transfer of ACE-inhibitors into the milk is probably low, and thus that ACE-inhibitor are likely to be safe during breastfeeding.

The objective of this trial is to collect information about the breast milk transfer, and subsequent infant exposure and general health outcome to selected maternal medication (ACE inhibitors) in patients from UZ Leuven. Furthermore, we will also use these data to verify the predictive performance of physiologically-based pharmacokinetic models to predict breast milk and subsequent neonatal exposure to maternal medication during lactation. The medicines that will be investigated are perindopril, captopril, cilazapril, enalapril, fosinopril, lisinopril, quinapril, ramipril and zofenopril.

The investigators will enroll +/-10 mothers, who have been prescribed ACE inhibitors for medical reasons and are breastfeeding their infant while taking this medication.The mother will be asked to collect milk samples during 24 h and 2 blood samples: one at the time of milk pumping the first time after medication intake, and one at the last pumping session of the 24 h. Furthermore, we will ask the parents if we can collect a blood sample of the child (1mL/kg, and max 2,5mL). In addition, clinical maternal and infant variables will be collected, as well as medication intake, sampling information and general infant health.

To conclude, with this study we hope to generate human data about the use of ACE inhibitors during breastfeeding. This information is an essential first step towards evidence-based risk assessment on the use of these drugs during lactation.

Inclusion Criteria:

For lactating mothers

• Lactating
• 0-6 months postpartum
• Age: ≥18 year
• On steady state ACE-inhibitor therapy, for any indication (e.g. perindopril, captopril, cilazapril, enalapril, fosinopril, lisinopril, quinapril, ramipril & zofenopril)
• Willing to express breast milk
• Informed consent to participate and for processing their personal data

For neonates/infants

• 0-6 months of age at inclusion of the mother
• Postmenstrual age: ≥ 37 weeks
• In case of blood sampling: exclusively breastfed at the time of sampling
• Parental informed consent to participate and for processing their personal data

Exclusion Criteria:

• Participation in a trial with an investigational product within the previous three months
• Not meeting the inclusion criteria