Sensitivity of the young infant to drug exposure through human milk

Psychoactive substances in human breast milk: a review of analytical strategies for their investigation

WHO recommends breastfeeding for the first 6 months of newborn's life. Due to its physicochemical properties, breast milk may contain undesirable components originated from mother's feeding, medication and illicit drugs consumption. Some of these substances transferred from bloodstream to milk and delivered to the infant can cause harmful effects. For the last decades, analytical advances enabled the analysis of several substances in milk using different techniques. Thereby, it is possible to evaluate infant's level of exposure to these substances. This review presents the information published in the main scientific dissemination media about psychoactive drugs investigation in human breast milk, involving the sample preparation techniques and chromatographic validated methods developed in the past 10 years.

Extent of medication use in breastfeeding women

BACKGROUND

The types of and extent to which medications are used by breastfeeding women have not been thoroughly investigated in the United States. The relationship between medication use during pregnancy and lactation has also been insufficiently investigated.

METHODS

A survey was given to a cohort of women who delivered their babies at a single center. The participants were asked to record the medications they had taken during pregnancy and subsequently were contacted each month during lactation to determine what medications they had taken.

RESULTS

Breastfeeding women took significantly more medications per month than pregnant women (p < 0.0001). Women who were breastfeeding also took prescription medications more frequently than women who were pregnant (p < 0.0001). The number of medications taken per month showed no trend throughout the course of breastfeeding. The medications most often used by breastfeeding women were multivitamins, nonsteroidal anti-inflammatory drugs, acetaminophen, progestins, antimicrobials, and decongestants. Over a third of the subjects took medications rated possibly or probably unsafe, or had unknown safety.

CONCLUSION

The women in this study took more prescription and nonprescription medications while breastfeeding than they did during pregnancy. Many of the medications taken have unknown safety for the breastfed infant. The results of this study should direct further research toward determining the safety of medications commonly used during lactation and to promote the labeling of these medications.

Neonatal exposure to drugs in breast milk

There are many benefits of breast-feeding both for the infant and for the mother. Nursing mothers who are also taking medications or exposed to environmental hazards may be confronted with a difficult choice to discontinue nursing or maternal medication or risk potential harm to the infant. Frequently, these decisions are made without sufficient information or understanding of the factors influencing exposure. The current review explores two indices of exposure, together with their pharmacokinetic determinants. Both of the indices include the milk to serum (M/S) concentration ratio for a given drug and the volume of milk consumed. The first exposure term, EI(Dose), expresses neonatal dose as a percentage of maternal dose and is inversely related to the maternal systemic clearance. By contrast, the second exposure term, EI(Conc), expresses infant concentration as a percentage of maternal concentration and is inversely related to the infant systemic clearance. Issues related to intersubject variation in M/S (e.g., colostrum vs. mature milk, fore vs. hind milk) and infant clearance (e.g., ontogeny of elimination pathways, pharmacogenetics) and their role in modulating exposure are also discussed.