Drug interactions between haloperidol and Seroquel

MONITOR: There is some concern that quetiapine may have additive adverse cardiovascular effects in combination with other drugs that are known to prolong the QT interval of the electrocardiogram. Data are conflicting. In clinical trials, there was no statistically significant difference between quetiapine and placebo in the proportions of patients experiencing potentially important changes in ECG parameters including QT, QTc, and PR intervals. However, QT prolongation has been reported in quetiapine overdose and with therapeutic use of other atypical antipsychotic agents such as sertindole, ziprasidone, and risperidone. In one case report, torsade de pointes arrhythmia developed in a patient treated with low-dose quetiapine. However, the relationship to quetiapine is uncertain, as there were multiple confounding risk factors such as hypomagnesemia, a history of QT prolongation (possibly prior to initiation of quetiapine), a history of substance abuse, and uncertain medication compliance. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Some clinicians recommend caution when quetiapine is administered concomitantly with drugs that prolong the QT interval, especially to patients with underlying risk factors. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, or syncope.