Jeanette, Macrobid, according to the United States Pharmacopeia: COMPLETE DRUG REFERENCE, 1994 edition (Consumer Reports Books, Publisher), is a brand name for nitrofurantoin, belonging to the family of medicines called anti-infectives commonly used to treat urinary tract infections. The following is excerpted from DRUGS IN PREGNANCY AND LACTATION, 4th edition (1994), Briggs, Freeman and Yaffe: BREAST FEEDING SUMMARY: "Nitrofurantoin is excreted into breast milk in very low concentrations. The drug could not be detected in 20 samples from mothers receiving 100 mg four times daily. In a second study, nine mothers were given 100 mg every 6 hours for one day, then either 100 mg or 200 mg the next morning. Only two of the four patients receiving the 200-mg dose excreted measureable amounts of nitrofurantoin, 0.3-0.5 ug/ml. Although these amounts are negligible, the authors cautioned that infants with glocose-6-phosphate dehydrogenase deficiency may develop hemolytic anemia from this exposure. The American Academy of Pediatrics considers nitrofurantoin to be compatible with breastfeeding." If you need the references, Jeanette, holler and I'll e-mail these to you. Jeanine Klaus, MS, IBCLC, LLLL Oakville, Ontario