Thiocolchicoside: review of adverse effects.

Thiocolchicoside has long been used as a muscle relaxant, despite a lack of proven efficacy beyond the placebo effect. Its chemical structure consists of colchicine, a sugar (ose) and a sulphur-containing radical (thio), and its adverse effects are therefore likely to be similar to those of colchicine. Using the standard Prescrire methodology, we reviewed the available data on the adverse effects of thiocolchicoside. 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.