Serotonin toxicity caused by an interaction between fentanyl and paroxetine.

Purpose: To report a case of serotonin toxicity, presenting in the postoperative period, caused by an interaction between paroxetine (a selective serotonin reuptake inhibitor, SSRI) and fentanyl (a phenylpiperidine opioid). Serotonin toxicity precipitated by fentanyl is unusual and has not previously been described in combination with SSRIs in the perioperative setting.