Is Flexeril (cyclobenzaprine) transmitted to the baby through breastmilk?

Cyclobenzaprine (Flexeril) Transmission Through Breastmilk

Yes, cyclobenzaprine is transmitted to babies through breastmilk, but in very low amounts with a calculated relative infant dose of only 0.5%, making it generally acceptable for short-term use in breastfeeding mothers when needed. 1

Transfer into Breastmilk and Safety Profile

• Cyclobenzaprine passes into human milk in small quantities
• Research shows low concentrations in breastmilk with a relative infant dose of 0.5% 1
• The FDA label notes caution should be exercised when administering cyclobenzaprine to nursing women, as it is structurally related to tricyclic antidepressants which are known to be excreted in human milk 2

Clinical Considerations for Breastfeeding Mothers

Recommendations for Use

• If muscle relaxation is needed, consider safer alternatives first:
  • NSAIDs like ibuprofen or naproxen are considered safe for breastfeeding mothers 3
  • Topical NSAIDs with or without menthol gel can be considered for muscle spasm management with minimal systemic absorption 3
  • Non-pharmacological approaches such as physical therapy, TENS, and appropriate rest should be tried first 3

If Cyclobenzaprine Must Be Used

• Use the lowest effective dose for the shortest duration possible
• For elderly patients, a lower starting dose of 5mg is recommended, which may also be prudent for breastfeeding mothers to minimize transfer 2
• Take the medication immediately after breastfeeding to maximize clearance time before the next feeding 3
• Monitor the infant for potential sedation, as cyclobenzaprine has sedative properties 1

Potential Risks and Monitoring

• Due to the sedative properties of cyclobenzaprine, regular clinical assessment of the infant is recommended 1
• Watch for signs of:
  • Excessive drowsiness
  • Poor feeding
  • Respiratory depression
  • Changes in sleep patterns

Important Precautions

• Extra caution should be taken when the nursing infant is less than 6 weeks of age due to immature hepatic and renal function 3
• Avoid combining cyclobenzaprine with:
  • Alcohol or other CNS depressants 2
  • MAO inhibitors (contraindicated) 2
  • SSRIs, SNRIs, TCAs, tramadol, bupropion, meperidine, verapamil (risk of serotonin syndrome) 2

Clinical Decision Algorithm

1. Assess if non-pharmacological treatments can manage the condition
2. If medication is necessary, consider NSAIDs or acetaminophen first
3. If a muscle relaxant is specifically required:
   • Use cyclobenzaprine at the lowest effective dose (5mg) for shortest duration
   • Time administration immediately after breastfeeding
   • Monitor infant for sedation or changes in behavior
   • Discontinue if any concerning symptoms develop in the infant

While cyclobenzaprine does transfer into breastmilk, the limited available data suggests that short-term use at appropriate doses presents minimal risk to most healthy, term infants.