Drug Interaction Report

MONITOR: Coadministration with glofitamab may increase the plasma concentrations of drugs that are substrates of CYP450 isoenzymes. Initiation of glofitamab treatment causes transient release of cytokines that may suppress CYP450 isoenzymes, although the potential for an interaction has not been studied. According to the manufacturer, the highest drug-drug interaction risk would be from the first dose on day 8 of cycle 1, up to 14 days after the first 30 mg dose on day 1 of cycle 2, as well as during and after cytokine release syndrome.

MANAGEMENT: Caution is advised when glofitamab is administered with drugs that are metabolized by CYP450 isoenzymes, particularly sensitive CYP450 substrates and/or 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 glofitamab as well as during and after cytokine release syndrome, and individual product labeling for the CYP450 substrate(s) should be consulted for specific dosage adjustment recommendations.

GENERALLY AVOID: Moderate-to-high dietary intake of potassium, especially salt substitutes, may increase the risk of hyperkalemia in some patients who are using angiotensin II receptor blockers (ARBs). ARBs can promote hyperkalemia through inhibition of angiotensin II-induced aldosterone secretion. Patients with diabetes, heart failure, dehydration, or renal insufficiency have a greater risk of developing hyperkalemia.

MANAGEMENT: Patients should receive dietary counseling and be advised to not use potassium-containing salt substitutes or over-the-counter potassium supplements without consulting their physician. If salt substitutes are used concurrently, regular monitoring of serum potassium levels is recommended. Patients should also be advised to seek medical attention if they experience symptoms of hyperkalemia such as weakness, irregular heartbeat, confusion, tingling of the extremities, or feelings of heaviness in the legs.