Breastfeeding and medications: drugs against bacteria, viruses and funguses

Many breastfeeding women seek medical care from general practitioners (GPs) for various health problems and GPs may consider prescribing medicines in these consultations. A lack of information from the manufacturers and of understanding the mechanics of drug transfer via human milk into the infant may lead to untimely cessation of breastfeeding or a breastfeeding mother may be denied medicines due to the possible risk to her infant, both of which may lead to unwanted consequences. With pathogen fighting drugs, actually, there isn’t much need for hesitation at all. Surpisingly few drugs need reconsideration about use in breastfeeding women and even fewer will need the mother to temporarily or definitely stop breastfeeding. With antibiotics it is always good to observe the infant for signs of diarrhea or thrush, because the antibiotics may destroy the yeast-restricting bacteria in the infant gut as well. Tetracyclines are probably safe for short duration and moderate doses, but should be avoided for high dosed and long term use. Breastfeeding needs to be postponed (bij expressing and discarding of the milk) for 1-3 days after the use of metronidazole and tinidazole. Maternal oral use of the antifungals nystatin, amphoterizin and fluconazole are all safe, the latter only reaching infant doses of 6-12% of the therapeutic dose used in premature infants.
Jayawickrama HS, Amir LH, Pirotta MV: GPs' decision-making when prescribing medicines for breastfeeding women: Content analysis of a survey. BMC Research Notes 2010, 3:82
Kristenson, J., & Ileth, K. (2007). Antibiotic, antifungal, antiviral, and antiretroviral drugs. In T. Hale, & P. Hartmann, Textbook of human lactation (pp. 513-521). Amarillo, Texas, USA: Hale Publishing L.P.