Drug Interactions between Meprozine and tebentafusp

ADJUST DOSE: The central nervous system and respiratory depressant effects of meperidine may be potentiated by concomitant use of other agents with CNS depressant effects. An increased risk of serious adverse reactions such as respiratory depression, hypotension, profound sedation, syncope, coma, and even death should be considered, particularly in elderly or debilitated patients.

MANAGEMENT: Caution and dosage adjustments are advisable when meperidine is used in combination with other narcotic analgesics, general anesthetics, phenothiazines, sedative-hypnotics, tranquilizers, tricyclic antidepressants, or other CNS depressants such as alcohol. A lower dosage of meperidine should be considered initially, then titrated carefully according to pain level and clinical response. Meperidine dosage reductions of 25% to 50% have been recommended for patients receiving phenothiazines and other tranquilizers. Patients should be advised to avoid rising abruptly from a sitting or recumbent position, and to notify their physician if they experience dizziness, lightheadedness, orthostasis, syncope, tachycardia, or excessive CNS effects that interfere with their normal activities. Patients should also avoid driving or operating hazardous machinery until they know how these medications affect them.

MONITOR: Coadministration with tebentafusp may increase the plasma concentrations of drugs that are metabolized by CYP450 pathways. The formation of hepatic CYP450 enzymes is down-regulated by increased levels of certain proinflammatory cytokines that are transiently released during initiation of tebentafusp treatment. Thus, tebentafusp may suppress CYP450 enzymes resulting in increased exposures of some CYP450 substrates. Clinical data are currently lacking but risk of an interaction is expected to be greatest during the first 24 hours of the first 3 tebentafusp doses.

MANAGEMENT: Caution is advised when tebentafusp is coadministered with drugs that are CYP450 substrates, particularly those with narrow therapeutic ranges (e.g., antiarrhythmics, anticonvulsants, immunosuppressants, theophylline) or sensitive substrates where increases in plasma levels may be significant or undesirable (e.g., statins, benzodiazepines, opioids). Clinical and/or laboratory monitoring should be considered following the initiation or withdrawal of tebentafusp, and the dosage(s) of the CYP450 substrate(s) adjusted accordingly.

MONITOR: It is uncertain whether tebentafusp causes clinically significant prolongation of the QT interval. According to the manufacturer, cases of QT interval prolongation were reported following tebentafusp treatment. 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. 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, hypocalcemia). Moreover, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Some authorities recommend caution if tebentafusp is coadministered with other agents known to prolong the QT interval. An ECG should be obtained before and after tebentafusp administration during the first 3 weeks of treatment and subsequently as clinically indicated. If the Fridericia-corrected QT interval (QTcF) exceeds 500 ms or increases by 60 ms or more from baseline, tebentafusp should be withheld and patients should be treated for any underlying precipitating factors (e.g., electrolyte abnormalities). Tebentafusp should be resumed once QTcF is less than 500 ms or less than 60 ms above baseline. Patients should be advised to seek prompt medical attention if they experience symptoms that indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.