[Breastfeeding and maternal medications].

OBJECTIVE To contribute with information about the adequate administration of drugs during breastfeeding. SOURCES OF DATA MEDLINE articles from 1993 to 2004, and Lilacs articles from 1995 to 2004 were selected in Portuguese, Spanish and English, by including the following keywords: breastfeeding, lactation, drugs and medicines. Other updated references found in articles and books were also included in this review, in order to provide additional information. SUMMARY OF THE FINDINGS Most of the drugs are compatible with breastfeeding. Few were considered inadequate, such as antineoplastic drugs, radiopharmaceuticals and drugs of abuse. Some drugs require concern, as they may cause adverse effects in breastfed babies or reduce the mother's breast milk volume. However, further knowledge on some medicines during lactation is required. CONCLUSION The fundamental principle in the prescription of medicines for lactating mothers is mostly based on the concept of risk and benefit. The option must be, as much as possible, for a drug that has already been studied, which is little released in the maternal milk or that does not mean an apparent risk for the infant's health. Medicines that reduce the mother's production of milk should be avoided during the lactation period. The use of galactogogos is reserved for particular situations. Therefore, only safety drugs should be administered during breastfeeding, which should rarely be discouraged or discontinued in such cases.