Skip to main content

Naloxone / pentazocine Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Jun 14, 2021.

Naloxone / pentazocine is also known as: Talwin Nx

Naloxone / pentazocine Pregnancy Warnings

Benefit should outweigh risk

US FDA pregnancy category: Not assigned

Risk Summary: Available data in pregnant women are insufficient to inform a drug-associated risk for major birth defects and miscarriage; based on animal data, a potential risk to the fetus cannot be ruled out.

-Prolonged use of opioids during pregnancy can result in physical dependence in the neonate; women should be advised of the risk of neonatal abstinence syndrome and ensure that appropriate treatment will be available.

Animal studies during the early gestational period have shown neural tube defects at 2.6 times the maximum daily dose (MDD). Administration of pentazocine-naloxone during organogenesis showed an increased incidence of resorptions and extra ribs at 0.2 times the MDD. Prolonged use of opioids during pregnancy for either medical or nonmedical use may cause physical dependence in the neonate and neonatal opioid withdrawal syndrome shortly after birth. Opioids cross the placenta and may produce respiratory depression in neonates (naloxone should be available for reversal of opioid-induced respiratory depression). There are no controlled data in human pregnancy.

Chronic opioid use may cause reduced fertility in males and females; it is unknown whether these effects on fertility are reversible.

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

Naloxone / pentazocine Breastfeeding Warnings

Pentazocine has been detected in human milk; newborn infants appear to be particularly sensitive to the effects of even small doses. No information is available on the excretion of naloxone, but it is not orally bioavailable and therefore it is unlikely to affect the breastfed infant. Studies in nursing mothers have shown that naloxone does not affect lactation hormone levels.

Once a mother's milk comes in, it is generally considered best to provide pain control with nonnarcotic analgesics. The developmental and health benefits of breastfeeding should be considered along with the mother's need for this drug and any potential adverse effects on the breastfed infant or underlying maternal condition. Withdrawal symptoms may occur in breastfed infants when maternal administration of an opioid analgesic is stopped or when breastfeeding is stopped.

Benefit should outweigh risk

Excreted into human milk: Yes (pentazocine); Unknown (naloxone)

-Prompt medical assistance should be sought for breastfed infants showing signs of increased sleepiness, difficultly breastfeeding, or limpness.

See references

References for pregnancy information

  1. "Product Information. Naloxone HCl-Pentazocine HCl (naloxone-pentazocine)." Actavis U.S. (Amide Pharmaceutical Inc) (2018):

References for breastfeeding information

  1. United States National Library of Medicine "Toxnet. Toxicology Data Network." (2013):
  2. "Product Information. Naloxone HCl-Pentazocine HCl (naloxone-pentazocine)." Actavis U.S. (Amide Pharmaceutical Inc) (2018):

Further information

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