Is Penicillin G safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Penicillin G. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
A breastfed 1-month-old infant with congenital syphilis developed a Herxheimer reaction 6 hours after its mother received 2.4 million units of benzathine penicillin G intramuscularly. However, the baby had also received 10 units of penicillin G at about the same time as the mother's injection. The reaction was possibly caused by penicillin in breastmilk.[ 5 ]
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
Maternal Levels. Ten women were given 100,000 units of penicillin G intramuscularly as a single dose or every 2 hours for 6 hours. Milk levels at 1 to 2 hours after the dose ranged from unmeasurable to 30 units/L after a single dose and an average of 50 units/L after multiple doses.[ 1 ] A single dose of penicillin G was given intramuscularly to 10 women. With doses of 200,000 units in 4 women, milk levels were about 60 units/L and were relatively constant for 6 hours after the dose. With doses of 500,000 units in 4 women, milk levels of penicillin reached 240 units/L at 2 to 4 hours after the dose. With 600,000 units in 2 women, peak levels of 240 to 360 units/L occurred at 4 hours after the dose.[ 2 ] After 2 doses of 2 million units of penicillin G intramuscularly in 15 women, peak milk levels were 120 units/L and trough levels were 10 units/L. After 2 doses of 4 million units of penicillin G intramuscularly in 5 women, peak milk levels were 220 units/L and trough levels were 30 units/L. With both doses, peak levels occurred 3 to 6 hours after the dose.[ 3 ] After a dose of 360 mg (about 550,000 units) of penicillin G intramuscularly in 2 women, milk levels averaged 0.35 mg/L (530 units/L) at 1 hour, 0.2 mg/L (300 units/L) at 2 hours, and 0.1 mg/L (150 units/L) at 4 hours after the dose. Only a trace was detectable at 6 hours after the dose.[ 4 ] Infant Levels. Relevant published information was not found as of the revision date.
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.