Is Flexeril (cyclobenzaprine) safe to use during breastfeeding?

Cyclobenzaprine (Flexeril) Safety During Breastfeeding

Cyclobenzaprine should be used with caution during breastfeeding due to lack of safety data and theoretical risk of infant sedation, with safer alternatives strongly preferred.

Key Safety Concerns

The FDA drug label explicitly states that "it is not known whether this drug is excreted in human milk" and recommends that "caution should be exercised when cyclobenzaprine hydrochloride is administered to a nursing woman" because cyclobenzaprine is structurally related to tricyclic antidepressants, some of which are known to transfer into breast milk 1.

Specific Risks to Consider

• Infant sedation risk: The American College of Obstetricians and Gynecologists notes the low but present risk of infant sedation when mothers use cyclobenzaprine 2
• Impaired maternal responsiveness: The American Academy of Pediatrics specifically advises avoiding co-sleeping if the mother is taking cyclobenzaprine, as her natural responsiveness may be inhibited 2
• CNS depression: Cyclobenzaprine enhances the effects of other CNS depressants, which could compound sedation risks 1

Strongly Recommended Safer Alternatives

First-line options for muscle spasm and pain in breastfeeding women:

NSAIDs (Preferred)

• Ibuprofen: Recommended by the American Society of Anesthesiologists as safe during breastfeeding 2
• Diclofenac: Also recommended as part of multimodal analgesia approaches 2
• Ketorolac: Safe with minimal transfer into breast milk and no demonstrable adverse effects in neonates, per the American College of Obstetricians and Gynecologists 2

Acetaminophen

• Paracetamol (acetaminophen): Considered compatible with breastfeeding by the American Academy of Pediatrics 2

Non-Pharmacological Approaches

• Physical therapy and heat/cold therapy: Considered safe alternatives for muscle spasm and pain in breastfeeding women by the American Society of Anesthesiologists 2

Clinical Decision Algorithm

If cyclobenzaprine use is being considered:

1. First, attempt safer alternatives: Use NSAIDs (ibuprofen, diclofenac) or acetaminophen combined with non-pharmacological therapies 2

2. If cyclobenzaprine is deemed necessary:

   • Inform the mother about the lack of safety data and theoretical sedation risk 1
   • Monitor the infant closely for excessive sedation, decreased alertness, or poor feeding 2
   • Strictly avoid co-sleeping arrangements 2
   • Use the lowest effective dose for the shortest duration 1

3. Consider timing: If a single dose is used, breastfeeding immediately before the dose may minimize infant exposure

Important Caveats

• Most medications appear in breast milk in only small amounts, and manufacturers often label drugs as prohibited during breastfeeding due to insufficient testing rather than demonstrated toxicity 3
• However, the structural similarity to tricyclic antidepressants and lack of specific lactation data for cyclobenzaprine warrant genuine caution 1
• The benefits of breastfeeding are substantial for both infant and maternal health, so women should not be discouraged from breastfeeding while taking compatible medications 3