Toxicity of Recreational Drugs and Medications During Lactation: A Systematic Review

Breastfeeding is recommended because of its benefits for the woman and the newborn, but during lactation, pre-existing or lactation-related health conditions that require medication can expose the minor to the risk of acute or chronic intoxication. While drug safety during pregnancy is a well-discussed topic, there is scarce evidence about the safety of common licit and illicit substances during breastfeeding. Hence, we performed a systematic review on the toxicity of licit and illicit substances during lactation. Applying PRISMA criteria for systematic reviews, we found 26 eligible papers published in the last ten years. Our review showed that human milk should be considered a specific (and dynamic) matrix for toxicological analysis, and relatively little is known about the actual levels of common substances in this matrix. Current recommendations on drug safety are mainly based on a benefit–risk ratio based on the little available information. Experimental research in this field should be promoted, which is also because of the relatively high frequency of sudden infant deaths that is currently unexplained.