warnings
WARNINGS QT Interval Prolongation ANZEMET prolongs the QT interval in a dose dependent fashion. Torsade de Pointes has been reported during post-marketing experience. Avoid ANZEMET in patients with congenital long QT syndrome, hypomagnesemia, or hypokalemia. Hypokalemia and hypomagnesemia must be corrected prior to ANZEMET administration. Monitor these electrolytes after administration as clinically indicated. Use ECG monitoring in patients with congestive heart failure, bradycardia, renal impairment, and elderly patients (see CLINICAL PHARMACOLOGY ). PR and QRS Interval Prolongation ANZEMET has been shown to cause dose dependent prolongation of the PR and QRS interval and reports of second or third degree atrioventricular block, cardiac arrest and serious ventricular arrhythmias including fatalities in both adult and pediatric patients. At particular risk are patients with underlying structural heart disease and preexisting conduction system abnormalities, elderly, patients with sick sinus syndrome, patients with atrial fibrillation with slow ventricular response, patients with myocardial ischemia or patients receiving drugs known to prolong the PR interval (such as verapamil) and QRS interval (e.g., flecainide or quinidine). ANZEMET should be used with caution and with ECG monitoring in these patients. ANZEMET should be avoided in patients with complete heart block or at risk for complete heart block, unless they have an implanted pacemaker (see CLINICAL PHARMACOLOGY ). Serotonin Syndrome The development of serotonin syndrome has been reported with 5-HT 3 receptor antagonists. Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin re-uptake inhibitors (SSRIs), serotonin and norepinephrine re-uptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, fentanyl, lithium, tramadol, and intravenous methylene blue). Some of the reported cases were fatal. Serotonin syndrome occurring with overdose of another 5-HT 3 receptor antagonist alone has also been reported. The majority of reports of serotonin syndrome related to 5-HT 3 receptor antagonist use occurred in a post-anesthesia care unit or an infusion center. Symptoms associated with serotonin syndrome may include the following combination of signs and symptoms: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, with or without gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of Anzemet and other serotonergic drugs. If symptoms of serotonin syndrome occur, discontinue Anzemet and initiate supportive treatment. Patients should be informed of the increased risk of serotonin syndrome, especially if Anzemet is used concomitantly with other serotonergic drugs (see DRUG INTERACTIONS , Patient Counseling Information ).