PIP: Drugs found in a woman's blood can be detected in her milk. The concentration in milk depends on the amount of drug in maternal blood, its lipid solubility and degree of ionization, whether it is actively secreted into the milk, and status of maternal renal function. Alcohol concentration in the mother's milk is generally about equal to that in her blood; it is not known however, how large a daily dose can be tolerated by an infant. Anticoagulants may or may not appear in breast milk. No significant side effects on the infant have yet been reported. Anticonvulsants generally do not affect infants, but some cause drowsiness and in one case, methemoglobinemia. Antihypertensive drugs such as reserpine may cause increased respiratory tract secretions, nasal congestion, cyanosis, and anorexia in breastfed infants, but others do not cause adverse side effects on the nursing infant. Antimicrobial, antithyroid, contraceptive hormones, norcotics, sedatives and psychiatric drugs, and caffeine cause minor and serious side effects on nursing infants. Generally, nursing mothers should refrain from taking drugs whenever possible. Those who must take antithyroid drugs (especially radioactive iodine), lithium, chloramphenicol and most anticancer drugs should not nurse. The side effects of many other drugs in breast milk are not known.