Trazodone's Medication Guide lists agitation, hallucinations, coordination problems, fast heartbeat, muscle rigidity, trouble walking, sweating, fever, nausea, vomiting, and diarrhea as symptoms of serotonin syndrome. It is most often triggered by combining trazodone with another serotonergic medication — such as an MAOI, SSRI, SNRI, triptan, tramadol, or certain supplements — without medical supervision.
This condition can progress quickly and requires emergency evaluation. Do not wait to see if symptoms resolve on their own if multiple signs appear together, especially fever and muscle rigidity.