Torsade de Pointes Associated With Laxative Abuse in a Patient Receiving Methadone

To the Editor: The risk factors of torsade de pointes are: drug-induced Q-Tc prolongation, female gender, hypokalemia, unrecognized congenital long Q-T syndrome (LQTS), and predisposing DNA polymorphisms.^1,2 These risk factors have not been studied in patients receiving methadone, a drug associated with Q-Tc interval prolongation, with a dose–effect relationship.^2,3 Also, drug-induced Q-Tc prolongation can be a potentially dangerous adverse effect of medication combinations. Most of the torsade de pointes caused by polypharmacy, including methadone, were reported in patients with human immunodeficiency virus (HIV). We report the case of a patient on stable methadone treatment, without HIV infection, whose condition suddenly worsened with hidden laxative abuse.

Case Report

“Ms. A,” a 46-year-old, white woman, had a history of cocaine and heroin dependence (discontinued 2 years ago, with negative urinary drug analysis) and cannabis dependence. She received methadone maintenance treatment, 80–200 mg/day for 4 years. The ECG recorded 3 months before the emergency department presentation was normal: Q-Tc 396 msec.

During her hospitalization to reduce methadone doses, while she received methadone 200 mg/day, the patient presented sudden death and was resuscitated after an episode of torsade de pointes. In the emergency department, the initial ECG on presentation showed ventricular tachycardia with torsade de pointes and Q-Tc 491 msec. The torsade de pointes resolved spontaneously. In the cardiac intensive care unit, she developed another episode of torsade de pointes. During hospitalization in the cardiology department, repetition of the ECG showed increased Q-Tc of 500 msec. The echocardiography found a left ventricular dysfunction (left ventricular ejection fraction: 20%−25%). Laboratory testing revealed hypokalemia (2.7 mmol/l). A treatment including ramipril and bisoprolol was started, and the patient’s condition improved. An empty box of laxatives (bisacodyl) was found in the patient's room. The patient acknowledged taking laxative to lose weight. She fulfilled DSM-IV-TR criteria for eating disorder, NOS.

Discussion

The cause of torsade de pointes is generally multifactorial. Our patient presented several risk factors for torsade de pointes: 1) female gender; 2) high doses of methadone; and 3) severe hypokalemia induced by hidden laxative abuse. Also, since the patient’s maternal grandmother died from sudden death, a congenital LQTS cannot be excluded.

This case highlights the need for carefully monitoring patients treated with methadone for potentially dangerous Q-T prolongation, which can occur even after the patients have been on therapy for some time. Patients should be informed that laxative use/abuse could lead to hypokalemia and increase their risk of developing a prolonged Q-T interval.³ ECG should be repeated to look for Q-Tc prolongation, but that may not be sufficient. Clinical investigations and ionograms could help to detect surreptitious laxative abuse.