What muscle relaxants are safe for breastfeeding mothers with minimal transfer into breastmilk?

Muscle Relaxants Safe During Breastfeeding

Neuromuscular blocking drugs and their reversal agents are generally safe for breastfeeding mothers as they have minimal transfer into breast milk and poor oral bioavailability in infants. 1

Safe Muscle Relaxants for Breastfeeding Mothers

Neuromuscular Blocking Agents

• Non-depolarizing neuromuscular blocking drugs (rocuronium, vecuronium, atracurium)

  • These are quaternary ammonium compounds with poor lipid solubility and oral bioavailability
  • They are ionized at physiological pH and will not be present in milk in significant amounts 1
  • Breastfeeding may resume once the mother has recovered from neuromuscular block

• Suxamethonium (succinylcholine)

  • Unlikely to be present in breast milk in significant amounts
  • Poor oral absorption with rapid elimination from maternal circulation
  • Ionized at physiological pH, limiting transfer to milk 1

Neuromuscular Blocker Reversal Agents

• Neostigmine

  • Quaternary ammonium compound with a half-life of 15-30 minutes
  • The amount transferred to breast milk is probably too small to be harmful 1
  • Safe for use in breastfeeding mothers

• Sugammadex

  • Large, highly polar molecule
  • Amount in milk likely very low with unlikely oral absorption by infant
  • Acceptable to use during breastfeeding 1
  • Note: Mothers taking oral hormonal contraceptives must follow "missed pill rules" after administration

Benzodiazepines (for Muscle Spasm)

• Midazolam (short-acting)

  • Extensive first-pass metabolism results in low systemic bioavailability
  • Blood levels in infant after breastfeeding expected to be low
  • Breastfeeding can resume after a single dose once mother has recovered 1

• Single-dose diazepam may be considered for procedures

  • Has active metabolite (desmethyl-diazepam) with prolonged half-life
  • Known to transfer in breast milk in significant levels
  • Acceptable as one-off dose but not for long-term use 1

Other Agents for Muscle Spasm

• Clonidine

  • Minimally secreted into milk
  • No reports of neonatal toxicity during breastfeeding
  • Note: May reduce prolactin secretion and potentially reduce milk production in early postpartum period 1

• Local anesthetics (lidocaine, bupivacaine)

  • May be secreted in small amounts in breast milk
  • Extensive investigation with no evidence of harm
  • Can be used without interrupting breastfeeding 1

Monitoring and Precautions

When using muscle relaxants:

• Resume breastfeeding once the mother has fully recovered from the effects of the medication
• For benzodiazepines, use the shortest-acting agent at the lowest effective dose
• Monitor infant for unusual drowsiness, poor feeding, or irritability
• For most agents, no waiting period is required before resuming breastfeeding

Special considerations:

• Single doses of most agents are generally safe
• Long-term use of benzodiazepines should be avoided when possible
• If a breastfeeding mother co-sleeps with her infant, natural responsiveness may be inhibited after receiving sedative medications 1

Clinical Decision Algorithm

1. Determine if muscle relaxant is needed for acute or chronic condition
2. For acute use: Select neuromuscular blockers or single-dose benzodiazepines
3. For chronic use: Consider non-pharmacological approaches first
4. If medication is necessary, select agents with:
   • Poor oral bioavailability
   • Short half-life
   • Minimal transfer to breast milk
5. Use lowest effective dose for shortest duration possible
6. Monitor infant for adverse effects

Most muscle relaxants used in clinical practice have minimal transfer to breast milk and pose little risk to the breastfeeding infant when used appropriately.