<P> Serotonin syndrome (SS) is a group of symptoms that may occur following use of certain serotonergic medications or drugs . The degree of symptoms can range from mild to severe . Symptoms include high body temperature, agitation, increased reflexes, tremor, sweating, dilated pupils, and diarrhea . Body temperature can increase to greater than 41.1 ° C (106.0 ° F). Complications may include seizures and extensive muscle breakdown . </P> <P> Serotonin syndrome is typically caused by the use of two or more serotonergic medications or drugs . This may include selective serotonin reuptake inhibitor (SSRI), serotonin norepinephrine reuptake inhibitor (SNRI), monoamine oxidase inhibitor (MAOI), tricyclic antidepressants (TCAs), amphetamines, pethidine (meperidine), tramadol, dextromethorphan, buspirone, L - tryptophan, 5 - HTP, St. John's wort, triptans, ecstasy (MDMA), metoclopramide, ondansetron, or cocaine . It occurs in about 15% of SSRI overdoses . It is a predictable consequence of excess serotonin on the central nervous system (CNS). Onset of symptoms is typically within a day of the extra serotonin . </P> <P> Diagnosis is based on a person's symptoms and history of medication use . Other conditions that can produce similar symptoms such as neuroleptic malignant syndrome, malignant hyperthermia, anticholinergic toxicity, heat stroke, and meningitis should be ruled out . No laboratory tests can confirm the diagnosis . </P> <P> Initial treatment consists of discontinuing medications which may be contributing . In those who are agitated benzodiazepines may be used . If this is not sufficient, a serotonin antagonist such as cyproheptadine may be used . In those with a high body temperature active cooling measures may be needed . The number of cases of serotonin syndrome that occur each year is unclear . With appropriate treatment the risk of death is less than one percent . The high - profile case of Libby Zion, who is generally accepted to have died from serotonin syndrome, resulted in changes to graduate medical education in New York State . </P>

All of the following are characteristics of serotonin syndrome except