Is metocarbamol (muscle relaxant) safe to use during breastfeeding?

Metocarbamol Safety During Breastfeeding

Metocarbamol can be used during breastfeeding with caution, as it is excreted in breast milk (confirmed in animal studies), but there are no human data on milk transfer or infant effects, making safer alternatives like ibuprofen or acetaminophen preferable for muscle spasm management.

FDA Labeling and Available Evidence

The FDA label for metocarbamol explicitly states that the drug and/or its metabolites are excreted in the milk of dogs, but it is unknown whether metocarbamol or its metabolites are excreted in human milk 1. Because many drugs are excreted in human milk, the FDA recommends caution when metocarbamol is administered to a nursing woman 1.

Key Limitations of Current Evidence

• No human studies exist documenting metocarbamol concentrations in breast milk 1
• No data are available on infant serum levels after maternal use 1
• No reports of adverse effects in breastfed infants have been published, but this reflects lack of study rather than proven safety 1

Safer Alternative Muscle Relaxants and Analgesics

If muscle relaxation or pain relief is needed during breastfeeding, consider these well-studied alternatives instead:

First-Line Options (Extensively Studied and Safe)

• Ibuprofen: Has been used extensively for postpartum pain and during lactation, and is considered safe during breastfeeding 2, 3
• Diclofenac: Small amounts detected in breast milk, used extensively during lactation and considered safe 2, 3
• Acetaminophen (Paracetamol): The amount an infant would ingest via breast milk is significantly less than pediatric therapeutic doses 2, 3
• Ketorolac: Low levels detected in breast milk without demonstrable adverse effects in neonates, compatible with breastfeeding 2, 3

Additional Safe Options

• Naproxen: Despite longer half-life, widely used after cesarean section with continued breastfeeding 2
• Celecoxib: Very low relative infant dose via milk, breastfeeding may continue 2

Clinical Decision Algorithm

When a breastfeeding woman presents with muscle spasm or musculoskeletal pain:

1. First choice: Use NSAIDs (ibuprofen or diclofenac) or acetaminophen, which have extensive safety data during breastfeeding 2, 3

2. If NSAIDs/acetaminophen are contraindicated or ineffective: Consider non-pharmacological approaches such as physical therapy and heat/cold therapy 3

3. If metocarbamol must be used (rare circumstances):

   • Use the lowest effective dose for the shortest duration 1
   • Monitor infant closely for sedation, drowsiness, or poor feeding (as metocarbamol causes CNS depression in adults) 1
   • Avoid co-sleeping, as maternal responsiveness may be inhibited 3
   • Consider timing doses immediately after breastfeeding to minimize infant exposure 4

Important Safety Considerations

• Metocarbamol possesses CNS-depressant effects and may cause drowsiness or dizziness in the mother 1
• The drug has combined effects with alcohol and other CNS depressants 1
• Most commonly used drugs transfer only small amounts into breast milk, generally much less than known safe pediatric doses 4
• The general principle is that drugs with good safety profiles in adults and established use during breastfeeding should be preferred over those with limited data 4, 5

Practical Counseling Points

• Reassure the mother that most medicines can be used safely during breastfeeding at recommended doses 5
• Explain that the lack of data on metocarbamol does not prove danger, but safer alternatives with extensive safety data exist 4
• If metocarbamol is prescribed, advise the mother to watch for infant sedation, poor feeding, or decreased responsiveness 1
• Contact a medical professional immediately if concerning infant symptoms develop 1