What muscle relaxant is safe for a breastfeeding mother?

Safe Muscle Relaxants for Breastfeeding Mothers

Neuromuscular blocking agents including suxamethonium, rocuronium, vecuronium, and atracurium are safe to use during breastfeeding due to their poor lipid solubility, poor oral bioavailability, and minimal transfer into breast milk. 1

First-Line Muscle Relaxant Options

• Neuromuscular blockers (suxamethonium, rocuronium, vecuronium, atracurium) are considered safe as they are quaternary ammonium compounds that are ionized at physiological pH and will not be present in milk in significant amounts 1
• Cyclobenzaprine can be used with caution as it shows low concentrations in breast milk with a calculated relative infant dose of only 0.5%, though regular monitoring of the infant for sedation is recommended 2
• Benzodiazepines (short-acting) like midazolam can be used for single doses as they have extensive first-pass metabolism resulting in low systemic bioavailability after oral doses 1

Safety Considerations for Specific Agents

Neuromuscular Blockers

• Suxamethonium: Unlikely to be present in breast milk in significant amounts due to ionization at physiological pH; has poor oral absorption with rapid elimination from maternal circulation 1
• Non-depolarizing agents (rocuronium, vecuronium, atracurium): Poor lipid solubility and oral bioavailability make them safe choices 1
• Breastfeeding can be resumed once the mother has recovered from neuromuscular block 1

Reversal Agents

• Neostigmine: A quaternary ammonium compound with a half-life of 15–30 minutes; amount transferred to breast milk is probably too small to be harmful 1
• Sugammadex: While no clinical data exists for breastfeeding, it's a large, highly polar molecule with likely very low amounts in milk and unlikely oral absorption by the infant 1

Benzodiazepines

• Midazolam: Preferred for single-dose use; breastfeeding can be resumed after a single dose once the mother has recovered 1
• Diazepam: Use with caution as it has an active metabolite (desmethyl-diazepam) with prolonged half-life; known to transfer in breast milk in significant levels 1

Analgesics That Can Be Used for Muscle Pain

• NSAIDs (ibuprofen, diclofenac, naproxen) are considered safe and compatible with breastfeeding 1, 3
• Paracetamol (acetaminophen) is safe as the amount an infant would ingest via breast milk is significantly less than pediatric therapeutic doses 1, 4
• Opioids should be used with caution:
  • Morphine is recommended if strong analgesia is required, but the infant should be monitored for sedation with repeated doses 1
  • Codeine should be avoided due to variable metabolism and risk of infant overdose 1
  • Tramadol requires observation of the child for unusual drowsiness 1

Monitoring and Precautions

• Monitor infants for signs of sedation, respiratory depression, or poor feeding, especially when using medications with sedative properties 1, 2
• Use the lowest effective dose for the shortest time possible 3, 4
• If possible, breastfeed before taking medication or avoid breastfeeding at times of peak drug concentration in milk 3
• For mothers using muscle relaxants, consider non-pharmacological approaches such as progressive muscle relaxation techniques which have been shown to improve breastfeeding outcomes 5, 6

Common Pitfalls to Avoid

• Avoid long-term use of benzodiazepines, especially diazepam, due to accumulation of active metabolites 1
• Don't use aspirin in analgesic doses (though low-dose aspirin for anti-platelet action can be used if strongly indicated) 1
• Avoid pethidine (meperidine) as repeated administration negatively affects the suckling infant 3, 4
• Don't assume all muscle relaxants have the same safety profile - always check specific drug properties and transfer into breast milk 1