The first example of a patient with etoricoxib‐induced immune hemolytic anemia

Abstract

Etoricoxib, a selective inhibitor of cyclooxygenase 2, is increasingly used in pain relief. Here, we report the first case of etoricoxib-induced immune hemolytic anemia. An 84-year-old male patient developed anemia 1 week after treatment with etoricoxib. There was no evidence of hemoglobinemia or hemoglobinuria. Administration of the drug was halted, and the patient recovered without further complications. The patient's red blood cells (RBCs) were found to be strongly coated with immunoglobulin G and C3d. Eluted antibodies and dialyzed serum from the patient were not reactive with untreated RBCs, but with etoricoxib-treated RBCs, RBCs in the presence of etoricoxib, urine containing drug metabolites (ex vivo antigen), and two of four additional COX inhibitor drugs analyzed. Although the causative antibodies were drug dependent usually leading to abrupt and intravascular hemolysis, the patient only gradually developed anemia. These findings together with a positive direct and indirect antiglobulin test may lead to confusion with autoimmune hemolytic anemia of warm type. A nonreactive eluate was the key serologic finding in identifying drug-induced immune hemolytic anemia in this case. Etoricoxib should be considered as a risk in the development of immune hemolytic anemia, with the causative antibodies potentially reacting with other COX inhibitors.