Clindamycin is present in breast milk.
The relative infant dose (RID) of clindamycin is 1.2% to 4.7% when calculated using the highest verifiable breast milk concentration located and compared to an infant therapeutic dose of 10 to 40 mg/kg/day. In general, breastfeeding is considered acceptable when the RID is <10%; when an RID is >25% breastfeeding should generally be avoided (Anderson 2016; Ito 2000). Using the highest verifiable milk concentration (3.1 mcg/mL), the estimated daily infant dose via breast milk is 0.465 mg/kg/day. This milk concentration was obtained following maternal administration of oral clindamycin 150 mg three times daily for at least 1 week (Stéen 1982). The manufacturer reports that clindamycin breast milk concentrations range from 0.7 to 3.8 mcg/mL (maternal dose, route, and duration not specified).
One case of bloody stools in an infant occurred after a mother received clindamycin while breastfeeding; however, a causal relationship was not confirmed (Mann 1980). In general, antibiotics that are present in breast milk may cause nondose-related modification of bowel flora.
According to the manufacturer, the decision to continue or discontinue breastfeeding during therapy should take into account the risk of infant exposure, the benefits of breastfeeding to the infant, and benefits of treatment to the mother. Additional guidelines recommend to avoid clindamycin in breastfeeding women if possible; monitor breastfeeding infants for GI disturbances, diarrhea, and bloody stools if maternal treatment is required (WHO 2002).