Is Flexeril (cyclobenzaprine) safe to use in a breastfeeding patient?

Cyclobenzaprine (Flexeril) Use During Breastfeeding

Cyclobenzaprine should be used with caution during breastfeeding, and safer alternatives like NSAIDs (ibuprofen, diclofenac) or acetaminophen should be strongly preferred for muscle pain and spasm. 1

Key Safety Concerns

The primary concern with cyclobenzaprine during lactation stems from limited data and its structural similarity to tricyclic antidepressants:

• Unknown milk excretion: It is not known whether cyclobenzaprine is excreted in human milk, and because it is closely related to tricyclic antidepressants (some of which are known to be excreted in breast milk), caution is warranted 2

• Risk of infant sedation: There is a low but present risk of infant sedation when cyclobenzaprine is used during breastfeeding 1

• CNS depressant effects: Cyclobenzaprine may enhance the effects of other CNS depressants, which could theoretically compound sedation risk in the nursing infant 2

Preferred Alternatives

Non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen are the first-line analgesics for breastfeeding women with muscle pain:

• Ibuprofen and diclofenac are considered safe during breastfeeding and are part of multimodal analgesia approaches 3, 1

• Acetaminophen (paracetamol) is compatible with breastfeeding 3, 1

• Ketorolac is also safe, with minimal transfer into breast milk and no demonstrable adverse effects in neonates 3

Non-Pharmacological Approaches

Physical therapy and heat/cold therapy are considered safe alternatives for muscle spasm and pain in breastfeeding women and should be prioritized when appropriate 1

Clinical Decision-Making Algorithm

If cyclobenzaprine must be used:

1. Ensure no safer alternative exists - NSAIDs, acetaminophen, or non-pharmacological approaches should be exhausted first 1

2. Use the lowest effective dose for the shortest duration possible 4

3. Monitor the infant closely for signs of sedation, drowsiness, and poor feeding 4

4. Time dosing strategically - administer before the infant's longest sleep interval to minimize exposure 4

5. Avoid co-sleeping if the mother is taking cyclobenzaprine, as her natural responsiveness may be inhibited 3

Important Caveats

• The elderly formulation guidance (starting at 5 mg and titrating slowly) suggests this medication has significant CNS effects that could theoretically affect infants through breast milk 2

• Most medications do reach breast milk in some amount, but generally in quantities much smaller than during pregnancy 5

• The decision should weigh the mother's therapeutic need against the theoretical risk to the infant, but in this case, equally effective and safer alternatives exist 1, 4