Cardiotoxic effects resulting from the interaction between risperidone and thiazide diuretics

Abstract

Atypical antipsychotics have their actions in doses that can cause important side effects. The risperidone is the new generation atypical antipsychotic most widely used these days and it is related to the treatment of schizophrenia, psychotic disorders, manic episodes and behavioral disorder, among others. The most significant side effects are associated with the central and autonomic nervous system, endocrine system and cardiovascular system. Considering the latter, negative inotropic effects and changes on eletrocardiograma can occur, with QT-interval prolongation, which can cause tachycardia and arrhythmias. We reported a case of a 48 years old man with history of persecutory delusion after being threatened at work, treated with risperidone and paroxetine. Since there was no improvement, the doses were increased and the patient showed QTc-interval prolongation, with a T-wave amplitude decrease and an increase on the U-wave, in addition to hypokalemia. Besides, the patient was hypertensive and was using hydrochlorothiazide. Risperidone has the potential to block the fast component of the cardiac potassium channel and it extends the repolarization process of the ventricles, which can lead to torsade de pointes, sudden cardiac death and arrhythmias. Also hydrochlo-rothiazide can cause hypokalemia, with disturbances on the myocardium depolarization and repolarization. There was a serious drug interaction with two potentially arrhythmogenic drugs, which led to the alterations on the electrocardiogram and generated hurtful symptoms to the patient. The shift of the atypical antipsychotic to one typical and of the hydrochlorothiazide to a diuretic that does not cause hypokalemia brought improvements to the patient.