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Bismuth subcitrate potassium / metronidazole / tetracycline Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Sep 14, 2021.

Bismuth subcitrate potassium / metronidazole / tetracycline is also known as: Pylera

Bismuth subcitrate potassium / metronidazole / tetracycline Pregnancy Warnings

Use is contraindicated.

US FDA pregnancy category: Not assigned.

Risk Summary: No data available on use of this drug or with bismuth subcitrate potassium in pregnant women to inform a drug-related risk. Tetracycline has been associated with permanent tooth discoloration and bone development inhibition when given during the second and third trimesters. Metronidazole has been associated with specific congenital anomalies.

-If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential harm to the fetus.
-Use of adequate methods of contraception should be encouraged.

Animal models given tetracycline have revealed evidence of reversible decreases in skeletal formation, yellow discoloration of bones and teeth, and embryotoxicity (when given early in development). Animal models given oral metronidazole have failed to reveal evidence of fetotoxicity; when given intraperitoneally, intrauterine deaths occurred. Animal studies with bismuth subcitrate potassium have not been reported. There are no controlled data in human pregnancy.

There are case reports of bone and teeth yellowing in infants exposed to tetracycline during the second and third trimesters; there are also reports of decreased fibula growth in premature infants, which resolved upon drug discontinuation. Greater than 2-gram IV doses given during pregnancy were correlated with maternal hepatotoxicity, which could result in premature or stillbirths. Metronidazole has been evaluated in over 5000 pregnant women.

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

Bismuth subcitrate potassium / metronidazole / tetracycline Breastfeeding Warnings

The effects of this drug on milk production are unknown.

Metronidazole is potentially tumorigenic and is known to be excreted into human milk. Infant metronidazole serum levels may be close to or comparable to therapeutic levels.

Tetracycline binds to calcium contained in milk.

Use should be avoided.

Excreted into human milk: Yes (metronidazole and tetracycline); Unknown (bismuth subcitrate)
Excreted into animal milk: Data not available (bismuth subcitrate)

-The effects in the nursing infant are unknown.
-Patients should discard milk produced during treatment and 2 days after completing treatment; infants should be fed stored milk (collected prior to treatment) and/or formula.

See references

References for pregnancy information

  1. "Product Information. Pylera (bismuth subcitrate potassium/metronidazo/TCN)." Aptalis Pharma (2022):

References for breastfeeding information

  1. United States National Library of Medicine "Toxnet. Toxicology Data Network." (2013):
  2. "Product Information. Pylera (bismuth subcitrate potassium/metronidazo/TCN)." Aptalis Pharma (2022):

Further information

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