Anaphylaxis
ELITEK may cause severe hypersensitivity reactions including anaphylaxis. ELITEK should be immediately and permanently discontinued in any patient developing clinical evidence of a serious hypersensitivity reaction (see WARNINGS, Anaphylaxis and ADVERSE REACTIONS, Immunogenicity).

Hemolysis
ELITEK administered to patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency can cause severe hemolysis. ELITEK administration should be immediately and permanently discontinued in any patient developing hemolysis. It is recommended that patients at higher risk for G6PD deficiency (e.g., patients of African or Mediterranean ancestry) be screened prior to starting ELITEK therapy (see CONTRAINDICATIONS and WARNINGS, Hemolysis).

Methemoglobinemia
ELITEK use has been associated with methemoglobinemia. ELITEK administration should be immediately and permanently discontinued in any patient identified as having developed methemoglobinemia (see WARNINGS, Methemoglobinemia).

Interference with Uric Acid Measurements
ELITEK will cause enzymatic degradation of the uric acid within blood samples left at room temperature, resulting in spuriously low uric acid levels. To ensure accurate measurements, blood must be collected into pre-chilled tubes containing heparin anticoagulant and immediately immersed and maintained in an ice water bath; plasma samples must be assayed within 4 hours of sample collection (see PRECAUTIONS, Laboratory Test Interactions).