The Food and Drug Administration (FDA) has granted emergency use authorization (EUA) to a combination of two monoclonal antibodies, casirivimab and imdevimab, for the treatment of mild to moderate COVID-19. The combination, which is administered intravenously, can be used in those who are at least 12 years of age, weigh at least 40 kg, and are at high risk for progression to severe COVID-19 and/or hospitalization. Monoclonal antibodies are laboratory-produced proteins that enhance or mimic the immune system.

Casirivimab and imdevimab should not be used in patients who are hospitalized or require oxygen therapy as a result of COVID-19, or who are receiving oxygen therapy for non-COVID-19-related reasons but require an increase in oxygen flow rate due to COVID-19. Monoclonal antibodies may be associated with worse outcomes if given to hospitalized patients using high-flow oxygen or needing mechanical ventilation because of COVID-19.

Data supporting the EUA come from a randomized, double-blind, placebo-controlled trial of 799 nonhospitalized adults with mild to moderate COVID-19 symptoms, of whom 266 received a single IV infusion of 2,400 mg of casirivimab and imdevimab (1,200 mg of each), 267 received 8,000 mg of casirivimab and imdevimab (4,000 mg of each), and 266 received a placebo, all within three days of obtaining a positive coronavirus test result. Viral load reduction was greater in those treated with casirivimab and imdevimab by day 7, compared with those receiving placebo. Additionally, fewer patients receiving monoclonal antibody therapy had ED visits and COVID-19 hospitalizations compared with patients given placebo (3% versus 9%) within 28 days of treatment. The casirivimab and imdevimab dose did not have an effect on the outcomes.

Possible adverse effects include anaphylaxis and infusion-related reactions, fever, chills, hives, itching, and flushing. An EUA does not indicate approval, only that the FDA considers the potential benefit of treatment to outweigh the potential risks based on the sum of current scientific knowledge, making it worthwhile to try the drug when there are no adequate, approved, and available treatment options. Because the therapy is not approved, there is no label for drug use. Instead, the FDA requires that a fact sheet be provided to health care providers and patients and caregivers that includes reconstitution and dosing instructions, criteria for who is considered high risk, potential adverse effects, and drug interactions. To read the fact sheet, see http://www.fda.gov/media/143892/download.

Nurses should be aware that casirivimab and imdevimab come in separate packages but must be combined into one IV infusion after dilution. Some packaging may indicate that the drugs can be given subcutaneously, but this should be ignored, as the EUA is only for IV infusion.

To read the "Dear Healthcare Provider" letter about preventing medication errors with casirivimab and imdevimab, go to http://www.fda.gov/media/143901/download.