Which muscle relaxants are safe for use during breastfeeding?

Muscle Relaxants Safe for Breastfeeding

Neuromuscular blocking agents used in anesthesia (suxamethonium, rocuronium, vecuronium, atracurium) are safe for breastfeeding mothers, as are benzodiazepines like midazolam for single-dose use. However, traditional oral skeletal muscle relaxants commonly prescribed for musculoskeletal pain have limited safety data during lactation.

Neuromuscular Blockers (Anesthesia Context)

The following neuromuscular blocking agents are compatible with breastfeeding 1:

• Suxamethonium - safe for use 1
• Rocuronium - safe for use 1
• Vecuronium - safe for use 1
• Atracurium - safe for use 1
• Neostigmine and sugammadex (reversal agents) - safe for use 1

These agents have poor oral bioavailability and short half-lives, making them compatible with breastfeeding 1.

Benzodiazepines (Muscle Relaxant Properties)

Safe Options

• Midazolam is the preferred benzodiazepine due to extensive first-pass metabolism resulting in low systemic bioavailability after oral doses 1, 2
• Breastfeeding can resume after a single dose of midazolam as soon as the mother has recovered from the procedure 1, 2
• Lorazepam and temazepam are shorter-acting alternatives preferred over diazepam 1, 2

Use With Caution

• Diazepam has an active metabolite (desmethyl-diazepam) with a prolonged half-life and transfers into breast milk in significant levels 1, 2
• Diazepam may be considered only as a one-off dose before a procedure, not for regular use 1, 2

Skeletal Muscle Relaxants (Oral Formulations)

Limited But Reassuring Data

• Cyclobenzaprine shows low concentrations in human milk with a calculated relative infant dose of 0.5% 3

• However, due to sedative properties, regular clinical assessment of the infant is recommended to evaluate for long-term effects 3

• Carisoprodol and its active metabolite meprobamate are excreted into breast milk 4

• One case report of high-dose carisoprodol (2800 mg/day) during breastfeeding showed only slight sedation in the infant with no withdrawal symptoms when nursing stopped 4

• Long-term neurobehavioral effects cannot be excluded 4

Insufficient Data

• Baclofen, tizanidine, metaxalone, orphenadrine, and methocarbamol lack adequate human lactation data 5, 6

Critical Safety Precautions

Mothers taking muscle relaxants or sedatives should avoid co-sleeping with their infant, as their natural responsiveness may be inhibited 1, 2.

Monitoring Requirements

• Observe the infant for signs of unusual drowsiness 1, 2
• Watch for poor feeding patterns 1, 2
• Contact a medical professional immediately if concerning symptoms develop 1, 2

Clinical Decision Algorithm

1. For procedural/anesthesia use: Neuromuscular blockers and single-dose midazolam are safe 1

2. For musculoskeletal pain in breastfeeding mothers:

   • First-line: NSAIDs (ibuprofen, diclofenac, naproxen) are extensively studied and safe 1
   • Second-line: If a muscle relaxant is essential, cyclobenzaprine has the most reassuring (though limited) lactation data with low milk transfer 3
   • Avoid: Regular use of diazepam or other long-acting benzodiazepines 1, 2

3. If prescribing any muscle relaxant: Counsel on avoiding co-sleeping and monitoring infant for sedation 1, 2

Important Caveats

• Few drugs are absolutely contraindicated during breastfeeding, but clear, safe, and reliable information is lacking for most skeletal muscle relaxants 5, 6
• The efficacy of long-term skeletal muscle relaxant use for chronic pain conditions like low back pain is questionable, with most showing no benefit over placebo 7, 8, 9
• Given limited efficacy data and uncertain safety profiles during lactation, consider whether the muscle relaxant is truly necessary or if alternative therapies (NSAIDs, physical therapy) would be more appropriate 9