What is the pregnancy category of Normix (Rifaximin)?

Rifaximin (Normix) Pregnancy Category

Rifaximin (Normix) is FDA pregnancy category C, indicating potential risks to the fetus, and should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. 1

Pregnancy Risk Classification

According to the FDA drug label information, rifaximin falls into pregnancy category C 1. This classification means:

• Animal reproduction studies have revealed adverse effects on the fetus
• There are no adequate and well-controlled studies in pregnant women
• The drug should be given only if the potential benefit justifies the potential risk to the fetus

Evidence of Risk in Animal Studies

The FDA label provides specific information about teratogenic effects observed in animal studies:

• Rifaximin was teratogenic in rats at doses 0.9 to 5 times the recommended human doses
• Teratogenic in rabbits at doses 0.7 to 33 times the recommended human doses
• Observed malformations included:
  • Cleft palate
  • Agnathia (absence of the jaw)
  • Jaw shortening
  • Hemorrhage
  • Eye abnormalities (partially open, small eyes)
  • Brachygnathia (shortened lower jaw)
  • Incomplete ossification
  • Increased thoracolumbar vertebrae 1

Clinical Considerations

• There are no available data on rifaximin use in pregnant women to inform any drug-associated risks
• The estimated background risk of major birth defects in the general U.S. population is 2-4%
• The estimated background risk of miscarriage in clinically recognized pregnancies is 15-20% 1

Potential Benefits in Specific Situations

Despite its category C classification, rifaximin may be considered in specific clinical scenarios:

• Because rifaximin is poorly absorbed systemically (less than 0.4%), it may have theoretical advantages over other antibiotics that have higher systemic absorption
• For treatment of infectious diarrhea in pregnant women, rifaximin might be considered when the benefits outweigh the risks, particularly when fluoroquinolones (which are contraindicated in pregnancy) would otherwise be used 2

Recommendations for Clinical Practice

When considering rifaximin use in pregnancy:

1. Assess the severity of the condition requiring treatment
2. Consider alternative treatments with better established safety profiles during pregnancy
3. If rifaximin is deemed necessary, use the lowest effective dose for the shortest duration
4. Counsel pregnant women about the potential risks to the fetus based on animal data
5. Document the benefit-risk discussion in the medical record

Breastfeeding Considerations

The FDA label also notes that there is no information regarding:

• The presence of rifaximin in human milk
• Effects on the breastfed infant
• Effects on milk production 1

The development and health benefits of breastfeeding should be considered along with the mother's clinical need for rifaximin and any potential adverse effects on the breastfed infant.