Muscles relaxants that are safe for lactating mothers
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Muscle Relaxants in Lactating Mothers
Muscle relaxants fall into two broad categories relevant here: neuromuscular blocking agents (NMBAs) used in anesthesia, and centrally/peripherally acting oral relaxants used for spasticity and musculoskeletal pain. Their safety profiles in lactation differ substantially.
1. Neuromuscular Blocking Agents (Surgical/Anesthesia Setting)
These are used intraoperatively and are considered safe for breastfeeding mothers. Per the ASA Statement on Resuming Breastfeeding after Anesthesia (updated October 2024):
| Drug | RID / Safety Note |
|---|---|
| Succinylcholine | Unknown RID; considered safe — highly polar molecule, unlikely to be secreted into breastmilk |
| Rocuronium | Unknown RID; considered safe — highly polar molecule |
| Vecuronium | Unknown RID; considered safe — highly polar molecule |
| Cisatracurium | Unknown RID; considered safe — highly polar molecule |
| Sugammadex (reversal) | Unknown RID; considered safe (though effect before breastfeeding is established is unknown) |
The rationale is pharmacokinetic: NMBAs are highly ionized, large, polar quaternary ammonium compounds with very poor oral bioavailability. Even if trace amounts entered milk, they would not be absorbed by the infant's GI tract.
Practice point: The ASA advises that breastfeeding can resume as soon as the mother is alert and awake — there is no need to "pump and dump" after general anesthesia with NMBAs.
2. Centrally Acting Oral Muscle Relaxants
✅ Relatively Safe / Use with Monitoring
Carisoprodol (Soma)
- LactMed lists this as an alternate drug to consider when cyclobenzaprine is needed. Excreted in milk; limited data, but widely referenced as preferred in some guidelines.
- Monitor infant for sedation.
Cyclobenzaprine (Flexeril)
- Per LactMed (updated January 2026): amounts in milk appear very small; two breastfeeding infants tolerated it without adverse effects (5 mg once daily and 10 mg twice daily in the mothers).
- Not a reason to discontinue breastfeeding if the mother requires it.
- ⚠️ One serious case: a 16-day-old exposed to cyclobenzaprine + acetaminophen + oxycodone developed bradycardia, hypotension, and respiratory arrest — the combination of CNS depressants is the key concern.
- Monitor infant for drowsiness, adequate weight gain, and developmental milestones. Extra caution in neonates, preterm infants, and when co-prescribed sedating drugs.
Baclofen
- Used for spasticity (MS, spinal cord injury). Excreted in breast milk in small amounts.
- LactMed considers short-term use acceptable; monitor infant for sedation and hypotonia.
- Case reports support use at low doses without significant infant effects.
Methocarbamol (Robaxin)
- Transfers into milk in small amounts. Limited data but generally considered low risk with short-term use at standard doses.
- MotherToBaby lists it as one of the agents with minimal expected infant exposure.
⚠️ Use with Caution / Insufficient Data
Tizanidine
- Alpha-2 agonist; limited lactation data. Theoretically low oral bioavailability in infants, but data are insufficient to confirm safety. Use only if clearly needed.
Diazepam / Benzodiazepines (sometimes used as muscle relaxants)
- RID ~0.3% per the ASA table — low, but benzodiazepines accumulate in neonates due to immature metabolism.
- Acceptable for single/short doses (e.g., procedural); avoid chronic use.
❌ Avoid or Use Only if Essential
Dantrolene
- Used for malignant hyperthermia and severe spasticity. Limited data in lactation; manufacturer advises caution. Not typically used long-term.
Orphenadrine, Chlorzoxazone, Metaxalone
- Insufficient lactation data. Avoid unless no alternatives.
Key Principles for Prescribing in Lactating Mothers
- Use the lowest effective dose for the shortest duration.
- Check the Relative Infant Dose (RID): An RID < 10% of the maternal weight-adjusted dose is generally considered safe.
- Timing: Having the mother take the drug immediately after breastfeeding and avoiding nursing at peak milk drug levels reduces infant exposure.
- Combinations are more dangerous than single agents: Cyclobenzaprine + opioids + benzodiazepines together pose serious infant CNS depression risk.
- Consult LactMed for the most current drug-specific data.
- Always weigh benefit to the mother against potential risk — untreated pain or spasticity also harms maternal wellbeing and indirectly affects the infant.
Disclaimer: Individual clinical decisions should account for infant age (neonates and preterm infants are higher risk), co-medications, and maternal dose. Consult LactMed and a clinical pharmacist for complex cases.
Is it safe to use myoril in lactating mothers
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The evidence is clear and consistent across all sources. Here is the answer:
Myoril (Thiocolchicoside) in Lactating Mothers
❌ Contraindicated — Do NOT Use
Myoril is the brand name for thiocolchicoside, a semisynthetic muscle relaxant derived from colchicine. It is explicitly contraindicated during breastfeeding based on regulatory and pharmacological grounds.
Reasons for Contraindication
1. Passes into Breast Milk
The European Medicines Agency (EMA) product information states clearly:
"Since it passes into the mother's milk, the use of thiocolchicoside is contraindicated during breastfeeding."
2. Aneugenic Metabolite (SL59.0955)
Preclinical studies revealed that a key metabolite of thiocolchicoside (SL59.0955) induces aneuploidy — an abnormal number of chromosomes in dividing cells — at concentrations close to those seen in humans at the standard oral dose of 8 mg twice daily. Aneuploidy is a risk factor for:
- Teratogenicity / embryo-fetal toxicity
- Spontaneous abortion
- Impaired male fertility
- Potential cancer risk
This is the primary reason the EMA mandated the contraindication in pregnancy, lactation, and even in women of childbearing potential not using contraception.
3. Risk of Convulsions
Thiocolchicoside acts on GABA-A receptors. Convulsions have been reported in susceptible individuals, which is a concern for breastfed infants who could be exposed via milk.
4. No Safety Data in Humans
There are no published human data on the actual levels of thiocolchicoside or its metabolites in breast milk. The e-lactation database confirms: "No published data were found on excretion into breast milk, but pharmacokinetic data favour excretion into breast milk."
What to Use Instead
If muscle relaxation is required in a lactating mother, consider safer alternatives (as discussed previously):
| Alternative | Notes |
|---|---|
| Methocarbamol | Low transfer into milk; short-term use acceptable |
| Cyclobenzaprine | Small amounts in milk; can be used with infant monitoring |
| Baclofen | Acceptable at low doses with infant monitoring for sedation/hypotonia |
| Ibuprofen + paracetamol | For musculoskeletal pain — very low milk transfer, preferred first-line |
| Physical therapy / heat | Non-pharmacological — always the safest option |
Bottom Line
Myoril (thiocolchicoside) must not be prescribed to breastfeeding mothers. The contraindication is regulatory (EMA-mandated), pharmacokinetic (confirmed milk passage), and toxicological (mutagenic metabolite). If a mother is already taking it, breastfeeding should be suspended and a safer alternative sought promptly.
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