Penicillin V is acceptable to use during breastfeeding. Limited information indicates that single maternal doses of penicillin V of 1320 mg produce low levels in milk that are not expected to cause adverse effects in breastfed infants. Occasionally, disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush, has been reported with penicillins, but these effects have not been adequately evaluated.
Milk penicillin V levels were measured in 16 women after an oral dose of 1320 mg. In 7 women with mastitis, peak milk levels averaged 0.06 mg/L (range 0.03 to 0.09 mg/L) in the breast with mastitis and 0.34 mg/L (range 0.15 to 0.51 mg/L) without mastitis. In 4 women without mastitis, peak milk levels averaged 0.26 mg/L (range 0.19 to 0.3 mg/L). In the women with mastitis, the peak level occurred 2.6 to 2.7 hours after the dose; in the women without mastitis, the peak occurred 5.4 hours after the dose. The authors estimated that an exclusively breastfed infant would receive an average dosage of about 50 mcg/kg/day (range 20 to 90 mcg/kg/day).
Nursing mothers were give a single oral dose of 1320 mg of penicillin V. In two of the infants who were breastfed, urine penicillin V was measured 2 hours after nursing. In one it was undetectable and in the other, the urine concentration was 520 mcg/L.
Effects in Breastfed Infants:
In one study, 12 infants were breastfed during maternal penicillin V therapy. Seven appeared normal, 3 had looser stools than normal, and 1 had a rash on the buttocks on the last day of therapy. These effects were possibly related to penicillin V in milk, but no control group was present. One infant had stains of blood in the stool, but it had happened once prior to maternal penicillin V treatment.
Possible Effects on Lactation:
Relevant published information was not found as of the revision date.
1. Matheson I, Samseth M, Loberg R et al. Milk transfer of phenoxymethylpenicillin during puerperal mastitis. Br J Clin Pharmacol. 1988;25:33-40. PMID:3130891
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