Drug Interactions between droperidol / fentanyl and Mellaril

MONITOR CLOSELY: The use of droperidol has been associated with QT interval prolongation, torsade de pointes and other serious arrhythmias, and sudden death. The concurrent administration of agents that can produce bradycardia, a known risk factor for QT interval prolongation, such as benzodiazepines and opiates, particularly intravenous opiates, may increase the risk of QT interval prolongation. In addition, hypotensive effects and central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking droperidol with benzodiazepines or opiates, especially in elderly or debilitated patients.

MANAGEMENT: Extreme caution and close monitoring are recommended if droperidol must be administered concomitantly with other bradycardic drugs. The dosage of droperidol should be individualized and titrated to the desired effect. Routine vital sign and ECG monitoring is recommended. When droperidol is used in combination with benzodiazepines or opiates, patients should be monitored for potentially excessive or prolonged CNS or respiratory depression as well as severe hypotension. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their doctor if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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CONTRAINDICATED: Thioridazine can cause dose-related prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. Thioridazine treatment alone has been associated with several reported cases of torsade de pointes and sudden death. 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). The extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s). In addition, certain agents with anticholinergic properties (e.g., sedating antihistamines; antispasmodics; neuroleptics; phenothiazines; skeletal muscle relaxants; tricyclic antidepressants; disopyramide) may have additive parasympatholytic and central nervous system-depressant effects when used in combination with thioridazine. Excessive parasympatholytic effects may include paralytic ileus, hyperthermia, mydriasis, blurred vision, tachycardia, urinary retention, psychosis, and seizures.

MANAGEMENT: Coadministration of thioridazine with other drugs that can prolong the QT interval is considered contraindicated.

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GENERALLY AVOID: Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants (e.g., nonbenzodiazepine sedatives/hypnotics, anxiolytics, muscle relaxants, general anesthetics, antipsychotics, other opioids, alcohol) may result in profound sedation, respiratory depression, coma, and death. The risk of hypotension may also be increased with some CNS depressants (e.g., alcohol, benzodiazepines, phenothiazines).

MANAGEMENT: The use of opioids in conjunction with benzodiazepines or other CNS depressants should generally be avoided unless alternative treatment options are inadequate. If coadministration is necessary, the dosage and duration of each drug should be limited to the minimum required to achieve desired clinical effect, with cautious titration and dosage adjustments when needed. Patients should be monitored closely for signs and symptoms of respiratory depression and sedation, and advised to avoid driving or operating hazardous machinery until they know how these medications affect them. Cough medications containing opioids (e.g., codeine, hydrocodone) should not be prescribed to patients using benzodiazepines or other CNS depressants including alcohol. For patients who have been receiving extended therapy with both an opioid and a benzodiazepine and require discontinuation of either medication, a gradual tapering of dose is advised, since abrupt withdrawal may lead to withdrawal symptoms. Severe cases of benzodiazepine withdrawal, primarily in patients who have received excessive doses over a prolonged period, may result in numbness and tingling of extremities, hypersensitivity to light and noise, hallucinations, and epileptic seizures.

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