What are the safe muscle relaxant options for lactating mothers?

Muscle Relaxants in Lactating Mothers

Direct Recommendation

Neuromuscular blocking agents used during anesthesia (suxamethonium, rocuronium, vecuronium, atracurium) are safe and compatible with breastfeeding, while cyclobenzaprine—the most commonly prescribed oral muscle relaxant—has minimal data but appears safe at low doses with infant monitoring. 1

Neuromuscular Blockers (Anesthesia Setting)

All neuromuscular blocking agents are compatible with breastfeeding and require no interruption of nursing. 1

• Suxamethonium, rocuronium, vecuronium, and atracurium are explicitly listed as safe for use during surgical procedures in lactating women 1
• These agents have poor oral bioavailability and do not pose risks to breastfed infants even when used during operative procedures 1
• Neostigmine (reversal agent) and sugammadex are also compatible with breastfeeding 1
• Breastfeeding may resume as soon as the mother has recovered sufficiently from anesthesia, with no waiting period required 1

Cyclobenzaprine (Oral Muscle Relaxant)

Cyclobenzaprine can be used cautiously during lactation, but requires infant monitoring due to its sedative properties and structural similarity to tricyclic antidepressants. 2, 3

• The FDA label states that cyclobenzaprine is closely related to tricyclic antidepressants (some of which are excreted in human milk), and caution should be exercised when administered to nursing women 2
• A 2019 study demonstrated low concentrations in human milk with a calculated relative infant dose of only 0.5%, which is well below the 10% safety threshold 3
• Due to sedative properties, regular clinical assessment of the infant is recommended to evaluate for drowsiness, poor feeding, and long-term effects 3
• If cyclobenzaprine is necessary, use the lowest effective dose (starting with 5 mg) for the shortest duration 2

Critical Safety Considerations

Mothers taking any sedating muscle relaxant should never co-sleep with their infant, as natural maternal responsiveness may be inhibited. 1, 4

• Extra caution is required for infants less than 6 weeks of age due to immature hepatic and renal function 4
• Preterm infants have the highest medication sensitivity and require heightened vigilance 4
• Monitor infants for unusual drowsiness, poor feeding, or decreased responsiveness when mothers use any sedating medication 1, 3

Alternative Pain Management Strategies

Multimodal analgesia with non-opioid drugs should be the first-line approach for musculoskeletal pain in lactating mothers. 1, 4

• Paracetamol and ibuprofen are the safest first-line options, compatible with immediate breastfeeding without any waiting period 1, 4, 5
• Other NSAIDs including diclofenac, naproxen, celecoxib, ketorolac, and parecoxib are also safe alternatives 1, 6
• These medications require no "pump and dump" and can be taken immediately before or after nursing 4, 5
• If opioid analgesia is required for severe pain, morphine is the preferred choice at the lowest effective dose for the shortest duration 1, 4, 6

Common Pitfalls to Avoid

• Do not assume all muscle relaxants are contraindicated—neuromuscular blockers used in anesthesia are completely safe 1
• Do not unnecessarily interrupt breastfeeding when using cyclobenzaprine if the relative infant dose is low and the infant is monitored 3
• Do not prescribe cyclobenzaprine without counseling mothers about infant monitoring for sedation 3
• Do not combine cyclobenzaprine with other serotonergic drugs (SSRIs, SNRIs, tramadol) without careful observation due to serotonin syndrome risk 2