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Torsades de Pointes Caused by a Small Dose of Risperidone in a Terminally Ill Cancer Patient

TO THE EDITOR: Delirium is a common complication in terminally ill cancer patients, and the palliation of delirious symptoms is important.¹ Risperidone, a new antipsychotic, has been increasingly used for delirious patients.² Risperidone is generally safe and has mild adverse effects in comparison with classical antipsychotics such as haloperidol and chlorpromazine but may cause QT-prolonged syndrome, which is associated with an increased risk of dysrhythmia and sudden cardiac death.^3–5 However, there have been no empirical reports on torsades de pointes syndrome induced by risperidone. Here, we report the first case of a terminally ill cancer patient who developed torsades de pointes syndrome after receiving risperidone for palliation of delirium.

Case Report
Ms. A, an 84-year-old woman with colon cancer, was admitted to our palliative care unit for symptom palliation of delirium and pain. On admission, she had somnolence, disorientation, mild psychomotor agitation, and was diagnosed with delirium according to DSM-IV. She received oral morphine and glibenclamide. She exhibited serious cachexia, and the abdomen was filled with a huge mass. Laboratory examinations revealed mild liver dysfunction (total bilirubin: 0.7 mg/dl; GOT: 49 IU; GPT: 39 IU; alkaline phosphatase: 355 IU) and hyperglycemia (663 mg/dl). Radiological examinations identified massive liver and intra-abdominal lymph node metastasis. ECG results were normal with corrected QT interval of 0.46 seconds. We attributed the underlying etiologies of delirium to morphine and hyperglycemia. Therefore, we replaced the daily 60-mg oral morphine regimen with 500 µg/day intravenous fentanyl and adjusted the sugar levels. In addition, Ms. A received oral risperidone, 0.5 mg/day, on days 5, 6, 9, and 11, when agitated. Pain and agitation were well controlled within a week.

On day 14, she suddenly complained of chest discomfort. Physical examination identified tachycardia at 200 bpm, and an ECG revealed polymorphic ventricular tachycardia (torsades de pointes). Immediately, she received 2.47 g of intravenous magnesium sulfate, and the rhythm became normal. A repeat ECG demonstrated normal sinus rhythm and the prolonged QT interval at 0.58 seconds. Laboratory examinations revealed deterioration of liver function (total bilirubin: 3.6mg/dl; GOT: 321 IU; GPT: 221 IU; alkaline phosphatase: 4280 IU), and electrolytes were all within normal limits (sodium: 138 meq/liter; potassium: 4.2 meq/liter; chloride: 104 meq/liter; calcium: 8.0 mg/dl). Ultrasonography identified obstruction of the bile duct.

Risperidone was discontinued, and a follow-up ECG on day 16 demonstrated normal corrected QT interval (0.45 seconds). Dysrhythmia did not recur. She died because of liver failure from the underlying malignancy. Bile drainage was not performed because of poor general conditions and her wishes.

Discussion
To date, there has been a single case report of sudden death after moderate doses of risperidone and several case reports of patients with QT prolongation syndrome.^3–5 To our knowledge, this is the first case of torsades de pointes occurring in a terminally ill cancer patient receiving a very small dose of risperidone.

Risperidone is mainly metabolized in the liver by CYP2D6 enzymes.³ The probable mechanisms of QT prolongation syndrome in this patient may involve liver dysfunction caused by the underlying malignancy, impaired metabolism, and the toxicity induced by elevated concentrations of unmetabolized risperidone.

This case illustrates that clinicians should note that risperidone may cause the prolongation of QT interval leading to dysrhythmia and sudden cardiac death in all patients with liver dysfunction, even if the dose is very low.

REFERENCES

1. Breitbart W, Jaramillo JR, Chochinov HM: Palliative and terminal care, in Psycho-oncology. Edited by Holland JC. New York, Oxford University Press, 1998, pp 437–449
2. Schwartz TL, Masand PS: The role of atypical antipsychotics in the treatment of delirium. Psychosomatics 2002; 43:171–174[Abstract/Free Full Text]
3. Ravine DS, Levenson JW: Fatal cardiac event following initiation of risperidone therapy. Ann Pharmacotherapy 1997; 31:867–870[Abstract]
4. Glassman AH, Bigger JH: Antipsychotic drugs: prolonged QTc interval, torsades de pointes, and sudden death. Am J Psychiatry 2001; 158:1774–1782[Abstract/Free Full Text]
5. Taylor DM. Antipsychotics and QT prolongation. Acta Psychiatr Scand 2003; 107:85–95[CrossRef][Medline]

Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Email this article to a Colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Articles & Searches Download to citation manager Citing Articles via Google Scholar Articles by Tei, Y. Articles by Miyata, H. Search for Related Content PubMed Citation Articles by Tei, Y. Articles by Miyata, H. Atypical Neuroleptics Cancer

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