Serotonin Syndrome From Duloxetine Monotherapy: A Case Report

Serotonin syndrome is a rare adverse reaction induced by serotonergic drugs. Most instances of the syndrome occur in the context of a serotonergic drug overdose and the combined use of monoamine oxidase inhibitors and other related drugs. We report a case of serotonin syndrome caused by duloxetine alone in an elderly Asian woman and review the literature. A 69-year-old woman was admitted to the hospital due to two months of irritability and reduced energy. She was diagnosed with depressive disorder in the outpatient department and took sertraline 75mg for one month, but there was no significant improvement of symptoms. After admission, sertraline was switched to duloxetine. After taking duloxetine 60mg, the patient developed confusion, inducible clonus, diaphoresis, tremor, hyperreflexia, and increased body temperature and blood pressure. Reviewing her history of drug exposure, physical examination, and associated laboratory tests, we ruled out other possible diseases and established a serotonin syndrome diagnosis. The symptoms and signs associated with serotonin syndrome disappeared within two days after treatments with hydration and diazepam and the withdrawal of duloxetine. Physicians should be watchful for serotonin syndrome, a rare, but in severe cases life-threatening, adverse drug reaction. It may occur with duloxetine monotherapy even at therapeutic doses.