Is cyclobenzaprine (a muscle relaxant) safe to use during breastfeeding?

Cyclobenzaprine Safety During Breastfeeding

Cyclobenzaprine can be used with caution during breastfeeding as it transfers into breast milk in low amounts with a calculated relative infant dose of only 0.5%. 1

Transfer into Breast Milk and Infant Exposure

• Cyclobenzaprine is a skeletal muscle relaxant that is structurally related to tricyclic antidepressants 2, 3
• Research shows that cyclobenzaprine transfers into human milk in low concentrations with a calculated relative infant dose of only 0.5% 1
• The FDA drug label notes that "it is not known whether this drug is excreted in human milk" and recommends caution due to its structural similarity to tricyclic antidepressants 2

Recommendations for Use During Breastfeeding

• Due to the sedative properties of cyclobenzaprine, regular clinical assessment of the infant is recommended to evaluate for potential effects 1
• Monitor breastfed infants for signs of:
  • Drowsiness or sedation 1, 3
  • Poor feeding 1
  • Changes in behavior 1

Dosing Considerations

• If cyclobenzaprine is needed during breastfeeding, consider using the lowest effective dose to minimize infant exposure 4
• A lower dose of 5 mg three times daily has been shown to be as effective as 10 mg three times daily with a lower incidence of sedation in adults 4
• The sedative effects of cyclobenzaprine are dose-related, so using lower doses may reduce the risk of sedation in both the mother and potentially the infant 4, 3

Pharmacological Considerations

• Cyclobenzaprine is a potent non-competitive antagonist of histamine H1 receptors, which likely contributes to its sedative effects 3
• It has a half-life of 18 hours in adults, which means it may accumulate with repeated dosing 4
• The drug has high lipid solubility, which can facilitate transfer into breast milk 1

Alternative Approaches

• For muscle spasm and pain in breastfeeding women, consider alternatives with established safety profiles first:
  • Non-pharmacological approaches (physical therapy, heat/cold therapy)
  • NSAIDs such as ibuprofen or diclofenac are considered safe during breastfeeding 5
  • Paracetamol (acetaminophen) is also considered safe during breastfeeding 5

Clinical Decision Making

• The decision to use cyclobenzaprine during breastfeeding should weigh:
  • The mother's need for pain relief and muscle relaxation
  • The low but present risk of infant sedation
  • The availability of safer alternatives 1, 6
• Most medicines can be used safely during breastfeeding at recommended doses, but caution is warranted with cyclobenzaprine due to its sedative properties 6

If cyclobenzaprine is used, mothers should be advised to observe their infant for unusual drowsiness or changes in feeding patterns and to contact a healthcare provider if these occur 1.