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Oxacillin Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Aug 9, 2023.

Oxacillin is also known as: Bactocill

Oxacillin Pregnancy Warnings

Animal studies have failed to reveal evidence of impaired fertility or fetal harm. 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.

This drug should be used during pregnancy only if clearly needed.

US FDA pregnancy category: Not assigned.

Risk summary: Although human experience with penicillins during pregnancy has shown no explicit proof of harmful effects on the fetus, such effects cannot be conclusively excluded.

See references

Oxacillin Breastfeeding Warnings

Use is considered acceptable; caution is recommended.

Excreted into human milk: Yes (in small amounts)

-Low levels in milk are not expected to cause harmful effects in the nursing infant.
-Disruption of infant's gastrointestinal flora (resulting in diarrhea or thrush) reported occasionally with penicillins, but such effects have not been adequately evaluated.

After 500 mg orally for 3 to 4 doses in 10 women, the highest level was 0.2 mg/L in 2 women 4 hours after dosing; in the other 8 women, milk levels were less than 0.2 mg/L between 1 and 3.75 hours after dosing.

A woman received 3 g orally daily; after the third dose, milk drug levels ranged from 0.04 to 0.1 mg/L, with peak level at 3 hours postdose. According to authors estimation, a breastfed infant would receive 0.3 mg/day of this drug in milk.

In 10 women with mastitis who received 1 g orally 3 times a day for 5 to 6 days, milk levels averaged from 0.43 to 0.68 mg/L. Urine from 6 of the breastfed infants was analyzed; drug was detectable in 5 of the 6 infants with urine levels ranging from 0.2 to 3.7 mg/L.

After 1 g IM every 6 hours for 6 to 9 days, 15 women with monolateral mastitis had peak milk drug levels of 0.49 mg/L (at 3 hours after the first dose on the first day) and 0.64 mg/L (at 6 hours after the last dose) in the healthy breast; the breast with mastitis had slightly lower levels.

After a single 500 mg IM dose in 2 women, milk levels ranged from 0.18 to 0.7 mg/L between 1 and 4 hours; the peak occurred 2 to 4 hours after dosing. At 6 hours after dosing, only a trace was detectable.

After a single 1 g IV dose in 15 women, milk levels averaged 0.68 mg/L at 2 hours after dosing.

See references

References for pregnancy information

  1. Product Information. Bactocill (oxacillin). SmithKline Beecham. 2001.

References for breastfeeding information

  1. Product Information. Bactocill (oxacillin). SmithKline Beecham. 2001.
  2. United States National Library of Medicine. Toxnet. Toxicology Data Network. 2013.

Further information

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