Abstract
A 41-year-old female with an eating disorder overdosed on 5,740 mg of paroxetine. She presented with fever, dilated pupils, increased tendon reflexes, opsoclonus, and myoclonus, and was diagnosed with serotonin syndrome. The day after admission, torsades de pointes (TdP) developed. Magnesium sulfate was administered, leading to the normalization of serum potassium and magnesium levels, but QTc prolongation persisted. The serum paroxetine level 7 days after the final administration was high. QTc interval gradually normalized as symptoms improved with the administration of benzodiazepine and cyproheptadine. This is the first reported case in which a high dose of paroxetine alone caused TdP. Paroxetine is considered to be relatively safe among selective serotonin reuptake inhibitor (SSRI). However, the dosage in the present case was markedly high. We suggest that the inhibition of CYP2D6 by the high-dose paroxetine elevated the serum concentration in a non-linear manner, causing TdP.
