Drug Interactions between Promethazine with Dextromethorphan and teclistamab

Using dextromethorphan together with promethazine may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

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MONITOR: Coadministration with teclistamab may increase the plasma concentrations of drugs that are substrates of CYP450 isoenzymes. Initiation of teclistamab treatment causes transient release of cytokines that may suppress CYP450 isoenzymes, although the potential for interaction has not been studied. According to the manufacturer, the highest drug-drug interaction risk would be from the start of teclistamab therapy (including the initial step-up dosing schedule) up to 7 days after the first treatment dose (considered to be the first weekly dose administered after the completion of the step-up dosing schedule), as well as during and after cytokine release syndrome.

MANAGEMENT: Caution is advised when teclistamab is coadministered with drugs that are metabolized by CYP450 isoenzymes, particularly those with a narrow therapeutic range, where minimal changes to concentration may lead to significant adverse reactions, such as carbamazepine, colchicine, cyclosporine, disopyramide, phenytoin, quinidine, theophylline, warfarin, macrolide immunosuppressants, vinca alkaloids, and some narcotic analgesics. Clinical and/or laboratory monitoring are recommended, particularly at the initial phase of treatment with teclistamab as well as during and after cytokine release syndrome, and the dosage(s) of the CYP450 substrate(s) adjusted accordingly.