Is Flexeril (Cyclobenzaprine) safe for a lactating woman to take for musculoskeletal pain?

Cyclobenzaprine and Breastfeeding Safety

Cyclobenzaprine (brand name Flexeril) should be used with extreme caution in lactating women, and alternative treatments should be strongly considered first, as the drug's excretion into breast milk is unknown and it is structurally related to tricyclic antidepressants that are known to be excreted in human milk. 1

Critical Safety Concerns for Lactation

• The FDA label explicitly states that it is not known whether cyclobenzaprine is excreted in human milk, and caution should be exercised when administering to nursing women 1
• Because cyclobenzaprine is closely related to tricyclic antidepressants (some of which are known to be excreted in human milk), there is theoretical risk of infant exposure through breastfeeding 1
• The drug's anticholinergic properties and CNS depressant effects raise concerns about potential sedation and other adverse effects in nursing infants 1

Safer Alternative Approaches for Musculoskeletal Pain

Non-Pharmacological First-Line Options

• The American College of Physicians recommends considering non-pharmacological approaches first, including rest and physical therapy, which carry no risk to the nursing infant 2
• Topical analgesics may provide relief with fewer systemic side effects and minimal breast milk transfer 2

Pharmacological Alternatives

• Scheduled acetaminophen may be effective for mild to moderate musculoskeletal pain and is considered compatible with breastfeeding 2
• NSAIDs (such as ibuprofen or naproxen) are generally considered compatible with breastfeeding and can be used for musculoskeletal pain 3
• If a muscle relaxant is absolutely necessary, consultation with a lactation specialist or clinical pharmacologist is essential to weigh risks versus benefits on a case-by-case basis

If Cyclobenzaprine Must Be Used

Dosing Considerations

• Use the lowest effective dose (5 mg three times daily) rather than higher doses to minimize potential infant exposure 2, 4
• Limit treatment duration to 7-14 days maximum, as muscle relaxants are only indicated for acute conditions 2
• Consider timing doses immediately after breastfeeding to minimize infant exposure at peak milk concentrations

Monitoring Requirements

• Monitor the infant closely for sedation, poor feeding, or other CNS effects 1
• Watch for anticholinergic effects in the infant, including constipation or urinary retention 1
• If any adverse effects are noted in the infant, discontinue the medication immediately

Important Clinical Pitfalls

• Never prescribe cyclobenzaprine for chronic pain conditions in any patient, as there is no evidence of benefit beyond 2-3 weeks 2
• The American College of Physicians reports that all muscle relaxants are associated with 50% higher total adverse events and double the CNS adverse events compared to placebo 2
• Avoid combining cyclobenzaprine with other serotonergic drugs (SSRIs, SNRIs, tramadol) due to risk of serotonin syndrome, which could affect both mother and potentially the infant 1
• Do not use cyclobenzaprine concurrently with MAO inhibitors due to life-threatening interactions 1