Is it safe to breastfeed while taking Bactrim (trimethoprim/sulfamethoxazole)?

Safety of Bactrim (Trimethoprim/Sulfamethoxazole) During Breastfeeding

Bactrim should be used with caution during breastfeeding and is considered possibly safe only in healthy term babies; it should be avoided in infants who are glucose-6-phosphate dehydrogenase deficient, jaundiced, or premature. 1

Risk Assessment

• Bactrim (trimethoprim/sulfamethoxazole) is contraindicated in nursing mothers with infants less than 2 months of age due to the risk of kernicterus (bilirubin-induced brain damage) 1, 2
• According to the FDA drug label, levels of sulfamethoxazole and trimethoprim in breast milk are approximately 2-5% of the recommended daily dose for infants over 2 months of age 2
• Caution should be exercised when Bactrim is administered to a nursing woman, especially when breastfeeding jaundiced, ill, stressed, or premature infants 2
• The European Respiratory Journal guidelines specifically note that Bactrim is "possibly safe" during breastfeeding but should be avoided in babies who are G6PD deficient, jaundiced, or premature 3

Potential Adverse Effects

• The sulfonamide component may cause hyperbilirubinemia in neonates due to displacement of bilirubin from plasma proteins 1, 2
• Risk of hemolytic anemia exists, particularly in G6PD-deficient infants 1
• Potential alteration of infant intestinal flora is a concern 3, 1
• May cause false-negative cultures if the infant develops a febrile illness while the mother is taking Bactrim 3, 1

Recommendations for Specific Populations

• Healthy term infants over 2 months of age: Bactrim is considered possibly safe 3, 2
• Infants under 2 months of age: Bactrim is contraindicated due to risk of kernicterus 2
• Infants with G6PD deficiency: Bactrim should be avoided 3, 1
• Jaundiced infants: Bactrim should be avoided 3, 1
• Premature infants: Bactrim should be avoided 3, 1

Alternative Antibiotics for Breastfeeding Women

If an antibiotic is needed during breastfeeding and Bactrim is contraindicated or concerning, consider these safer alternatives:

• Penicillins and aminopenicillins (e.g., amoxicillin) are considered compatible with breastfeeding 1, 4
• Cephalosporins are considered compatible with breastfeeding 1, 4
• Macrolides (e.g., azithromycin) are probably safe, though there is a very low risk of hypertrophic pyloric stenosis if used during the first 13 days of breastfeeding 3, 1

Practical Considerations

• If Bactrim must be used in a breastfeeding mother with a healthy term infant over 2 months of age, monitor the infant for unusual symptoms including jaundice, diarrhea, or rash 1, 5
• When possible, time medication administration immediately after breastfeeding to minimize drug concentration in milk during the next feeding 5
• The CDC recommends that trimethoprim-sulfamethoxazole can be used during breastfeeding in mothers with infants older than 2 months who are healthy and not G6PD deficient 3
• The benefits of breastfeeding should be weighed against the potential risks of the medication, with consideration of alternative antibiotics when appropriate 4, 6