Rare case of serotonin syndrome with therapeutic doses of paroxetine.

Paroxetine (Paxil) is a selective serotonin reuptake inhibitor (SSRI) and anxiolytic that is approved to treat numerous mood disorders. Serotonin syndrome, defined as a triad of mental status changes, autonomic instability, and neuromuscular abnormalities, is a potentially life-threatening complication of administering such serotonin-modifying drugs. Most cases of serotonin syndrome that have occurred with paroxetine administration are due to inadvertent drug interactions, most notably between SSRIs and monamine oxidase inhibitors, or intentional overdoses. The authors present the case of an 80-year-old woman who presented with serotonin syndrome while on a therapeutic dose of paroxetine. Paroxetine was stopped, and aggressive hydration with fluids and treatment with cyproheptadine was followed by remarkable improvement and return to baseline status in 4 days. This case illustrates the importance for physicians to have a heightened sense of suspicion of the serotonin syndrome in any patient known to be on serotonin-modifying agents presenting with altered sensorium and cholinergic symptoms. Consequently, they will be able to start timely treatment without subjecting the patient to unnecessary and potentially harmful tests.