In order to reach a diagnosis of serotonin syndrome, a history of use of a serotonergic agent, recognized signs and symptoms, and the exclusion of other conditions are required.2,8,9 Serotonin syndrome involves mental, autonomic and neurological disorders of sudden onset less than 24 hours after the beginning of treatment or an overdose.2,3,4,6,7,8,9 The diagnosis of serotonin syndrome is guided by the Sternbach criteria14 but is still difficult in cases of benign symptoms or normal neurological test results.3,9,15 Radomski and colleagues9 have revised these criteria and classified serotonin syndrome as a mild state of serotonin-related symptoms, or serotonin syndrome (full-blown form) (4 major symptoms or 3 major ones plus 2 minor ones) (Box 1) or toxic (coma, generalized tonic-clonic seizures, fever that might exceed 40°C).3,9