Thiocolchicoside

Thiocolchicoside (Muscoril, Myoril, Neoflax) is a muscle relaxant with anti-inflammatory and analgesic effects. It acts as a competitive GABAA receptor antagonist and also glycine receptor antagonist with similar potency and nicotinic acetylcholine receptors to a much lesser extent. It has powerful convulsant activity and should not be used in seizure-prone individuals.
Side effects.
Side effects of thiocolchicoside can include nausea, allergy and vasovagal reactions.
Liver injury, pancreatitis, seizures, blood cell disorders, severe cutaneous disorders, rhabdomyolysis, and reproductive disorders have all been recorded in the French and European pharmacovigilance databases and in the periodic updates that the companies concerned submit to regulatory agencies. These data do not specify the frequency of the disorders nor do they identify the most susceptible patient populations. Thiocolchicoside is teratogenic in experimental animals and also damages chromosomes. Human data are limited to a follow-up of about 30 pregnant women (no major malformations) and reports of altered spermatogenesis, including cases of azoospermia. In practice, there is no justification for exposing patients to the adverse effects of thiocolchicoside. It is better to use an effective, well-known analgesic for patients complaining of muscle pain, starting with paracetamol.
Although muscle relaxants may have the major side effect of sedation, thiocolchicoside is free from sedation effects possible due to non-interference with nicotinic receptors.
Pharmacokinetics.
Thiocolchicoside is broken down in the body to a metabolite called 3-demethylthiocolchicine (also known as SL59.0955 or M2) that could damage dividing cells therefore inducing toxicity in the embryo, neoplastic changes and fertility reduction in males. Therefore, recommended oral dose should not exceed 7 days and intramuscular dose duration should not exceed 5 days. Local skin preparations are less toxic.