Cyclobenzaprine (Flexeril) During Breastfeeding
Cyclobenzaprine should be used with caution during breastfeeding, and safer alternatives like acetaminophen or ibuprofen should be strongly preferred for pain management.
Key Safety Concern
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.
Why This Matters
Lack of safety data: Unlike well-studied medications that are confirmed compatible with breastfeeding, cyclobenzaprine has no established safety profile during lactation 1.
Structural concerns: Its close relationship to tricyclic antidepressants raises theoretical concerns about infant exposure and potential sedating effects 1.
Anticholinergic properties: Cyclobenzaprine has atropine-like actions that could theoretically affect the infant, though this has not been studied 1.
Recommended Safer Alternatives
For pain management during breastfeeding, the following medications have established safety profiles:
Acetaminophen (paracetamol): Considered fully compatible with breastfeeding and is a preferred first-line analgesic 2, 3, 4.
Ibuprofen: Extensively studied and confirmed safe during breastfeeding with minimal transfer to breast milk 2, 5, 3, 4.
Other NSAIDs: Diclofenac, naproxen, and ketorolac are also compatible options 2, 5.
Multimodal approach: Combining non-opioid analgesics (acetaminophen plus an NSAID) provides effective pain control without the uncertainty of cyclobenzaprine 2.
Clinical Decision-Making Algorithm
If muscle relaxation is specifically needed:
First, optimize non-pharmacologic approaches (physical therapy, heat/ice, rest).
Use acetaminophen and/or ibuprofen as first-line agents, as these provide both analgesic and anti-inflammatory effects 2, 3.
If cyclobenzaprine is deemed absolutely necessary, use the lowest effective dose for the shortest duration possible 2.
Monitor the infant closely for unusual sedation, drowsiness, or feeding difficulties 2.
Consider timing doses immediately after breastfeeding to minimize infant exposure 3.
Important Caveats
Most medications are actually compatible with breastfeeding, and the benefits of continued breastfeeding typically outweigh theoretical medication risks 3, 6, 7.
However, when safer alternatives with established safety data exist (as they do for pain management), these should always be prioritized over medications with unknown lactation profiles 3, 4.
The common practice of unnecessarily interrupting breastfeeding due to excessive caution should be avoided, but this does not apply when well-studied alternatives are readily available 7.