Acute toxicity profile of tolperisone in overdose: Observational poison centre-based study.

INTRODUCTION Tolperisone is a centrally acting muscle relaxant that acts by blocking voltage-gated sodium and calcium channels. There is a lack of information on the clinical features of tolperisone poisoning in the literature. The aim of this study was to investigate the demographics, circumstances and clinical features of acute overdoses with tolperisone. METHODS An observational study of acute overdoses of tolperisone, either alone or in combination with one non-steroidal anti-inflammatory drug in a dose range not expected to cause central nervous system effects, in adults and children (< 16 years), reported to our poison centre between 1995 and 2013. RESULTS 75 cases were included: 51 females (68%) and 24 males (32%); 45 adults (60%) and 30 children (40%). Six adults (13%) and 17 children (57%) remained asymptomatic, and mild symptoms were seen in 25 adults (56%) and 10 children (33%). There were nine adults (20%) with moderate symptoms, and five adults (11%) and three children (10%) with severe symptoms. Signs and symptoms predominantly involved the central nervous system: somnolence, coma, seizures and agitation. Furthermore, some severe cardiovascular and respiratory signs and symptoms were reported. The minimal dose for seizures and severe symptoms in adults was 1500 mg. In 11 cases the latency between the ingestion and the onset of symptoms was known and was reported to be 0.5-1.5 h. CONCLUSIONS The acute overdose of tolperisone may be life-threatening, with a rapid onset of severe neurological, respiratory and cardiovascular symptoms. With alternative muscle relaxants available, indications for tolperisone should be rigorously evaluated.