Should we continue Zerodol TH SOS (thiocolchicoside) and T. Myoril 1-0-1 (thiocolchicoside and tolperisone) in a patient with respiratory issues and muscle spasms?

Should Zerodol TH and Myoril Be Continued in This Patient?

Discontinue both Zerodol TH (thiocolchicoside) and Myoril (tolperisone/thiocolchicoside combination) immediately in any patient with respiratory issues, as thiocolchicoside lacks proven efficacy beyond placebo and carries significant safety risks including seizures, blood disorders, and reproductive toxicity, while muscle relaxants can worsen respiratory function. 1

Critical Safety Concerns with Thiocolchicoside

Lack of Efficacy and Significant Adverse Effects

• Thiocolchicoside has never demonstrated efficacy beyond placebo effect for muscle relaxation, making its use unjustifiable given its adverse effect profile 1
• Recent animal studies confirm thiocolchicoside at both 2 mg/kg and 4 mg/kg doses showed no skeletal muscle relaxant activity and failed to potentiate the effects of standard muscle relaxants like diazepam 2
• The drug's chemical structure is derived from colchicine, predisposing it to similar serious adverse effects 1

Documented Serious Adverse Events

• Liver injury, pancreatitis, seizures, blood cell disorders, severe cutaneous reactions, and rhabdomyolysis have all been recorded in French and European pharmacovigilance databases 1
• Thiocolchicoside is teratogenic in animals and damages chromosomes, with the European Medical Agency restricting its use to maximum 7 days orally or 5 days by injection due to production of metabolite M2 that can cause aneuploidy 1, 2
• Reproductive toxicity includes altered spermatogenesis and cases of azoospermia in men 1

Respiratory Contraindications

Muscle Relaxants and Respiratory Function

• In patients with respiratory compromise, any centrally acting muscle relaxant poses risk of respiratory muscle weakness 3
• The American Thoracic Society guidelines for neuromuscular disease emphasize that respiratory muscle function must be preserved, and medications that could impair respiratory muscles should be avoided 3
• Muscle spasms listed as adverse effects in multiple drug classes suggest these agents can paradoxically worsen muscle function 3

Specific Respiratory Risks

• Patients with COPD or other respiratory conditions require careful assessment of medications that could worsen respiratory muscle strength 3
• Neurotoxicity from muscle relaxants can interact with respiratory muscle function, particularly in compromised patients 3

Alternative Management Strategy

Preferred First-Line Approach

• Use paracetamol (acetaminophen) as the first-line analgesic for muscle pain, as it is effective and well-known with a favorable safety profile 1
• Paracetamol remains the safest option for musculoskeletal pain management across diverse patient populations 4

If Additional Therapy Needed

• Consider physical therapy, airway clearance techniques, and respiratory support as appropriate for the underlying respiratory condition 3
• NSAIDs can be considered if not contraindicated by the patient's specific respiratory or cardiovascular condition, though they should be used cautiously 4
• Avoid all centrally acting muscle relaxants in patients with respiratory compromise 3

Common Pitfalls to Avoid

• Do not continue thiocolchicoside simply because it was previously prescribed - the evidence clearly shows lack of efficacy and significant safety concerns 1, 2
• Do not assume combination products are more effective - the addition of thiocolchicoside to tolperisone provides no additional benefit 2
• Do not overlook respiratory status when prescribing muscle relaxants - respiratory muscle weakness can be life-threatening in compromised patients 3
• Do not use these medications for more than 7 days even in patients without respiratory issues due to chromosomal damage risk 1, 2