Skip to main content

Penicillin g potassium Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Apr 28, 2023.

Penicillin g potassium is also known as: Pfizerpen

Penicillin g potassium Pregnancy Warnings

This drug should be used during pregnancy only if clearly needed; it has been used without apparent harmful effects.

US FDA pregnancy category: Not assigned.

Risk summary: Malformative risk with use of this drug in pregnant women is unlikely.

Animal studies have failed to reveal evidence of fetal harm. No positive evidence of adverse effects on the fetus observed during human use of penicillins; however, there are no controlled data in human pregnancy.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

See references

Penicillin g potassium Breastfeeding Warnings

Use is considered acceptable; caution is recommended.

Excreted into human milk: Yes

-The effects in the nursing infant are unknown.
-Limited data indicate that low levels in milk are not expected to cause harmful effects in nursing infants.
-Disruption of infant's gastrointestinal flora (resulting in diarrhea or thrush) reported occasionally with penicillins; such effects have not been adequately evaluated.

Single or multiple doses of penicillin G (100,000 units once or every 2 hours for 6 hours) were administered to 10 women. At 1 to 2 hours after dosing, milk levels ranged from unmeasurable to 30 units/L after a single dose and averaged 50 units/L after multiple doses.

A single IM dose of penicillin G was administered to 10 women. Milk levels were about 60 units/L and relatively constant for 6 hours after a 200,000-unit dose in 4 women. At 2 to 4 hours after a 500,000-unit dose in 4 women, milk levels reached 240 units/L. Peak levels of 240 to 360 units/L occurred at 4 hours after a 600,000-unit dose in 2 women.

After 2 IM doses (2 million units/dose) of penicillin G in 15 women, peak and trough milk levels were 120 and 10 units/L, respectively. After 2 IM doses (4 million units/dose) in 5 women, peak and trough milk levels were 220 and 30 units/L, respectively. Peak levels occurred 3 to 6 hours postdose.

After an IM dose of 360 mg (about 550,000 units) of penicillin G 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 dosing; at 6 hours postdose, only a trace was detectable.

A Herxheimer reaction occurred in a 1-month-old breastfed infant with congenital syphilis 6 hours after a 2.4 million-unit IM dose of benzathine penicillin G was administered to the mother; the infant had also received 10 units of penicillin G at about the time of the maternal dose. The reaction was possibly due to penicillin in breast milk.

See references

References for pregnancy information

  1. Product Information. Pfizerpen (penicillin). Roerig Division. 2001.

References for breastfeeding information

  1. Product Information. Pfizerpen (penicillin). Roerig Division. 2001.
  2. National Library of Medicine (US). Drugs and Lactation Database (LactMed) 2019.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.