ABSTRACT
We reported a case of acute intoxication by tramadol and zolpidem, resulting in QT prolongation in a patient. A 38-year-old male patient presented to the emergency department (ED) because of poisoning from 3 g of tramadol and 50 mg of zolpidem 4 hours before. During supportive treatment, he developed QT prolongation without clinical manifestations. He was discharged 5 days after admission without any sequelae. We measured the blood and urine concentrations of tramadol and zolpidem at various time points, which revealed a blood tramadol concentration-dependent change in QT intervals and an increased blood tramadol concentration at 8 hours after the ED visit. Tramadol and zolpidem were metabolized by the same enzyme, cytochrome P450 3A4. Therefore, competitive inhibition may increase drug toxicity. In addition, the blood concentration of tramadol may increase and result in QT prolongation even after appropriate initial treatment.