title: Immediate and delayed allergic reactions to Crotalidae polyvalent immune Fab (ovine) antivenom.
abstract: Allergic reactions are the most commonly reported adverse events after administration of antivenoms. Conventional horse serum-based crotalid antivenom used in the United States (Antivenin [Crotalidae] polyvalent) can lead to both immediate and delayed hypersensitivity reactions. Crotalidae polyvalent immune Fab (ovine) (CroFab; FabAV) has recently been approved for use in the United States. Experience from premarketing trials of this product and in the administration of other types of Fab, such as in digoxin poisoning, has demonstrated these fragments to be safe and effective, with a low incidence of sequella; however, allergic reactions can occur when any animal-protein derivatives are administered to human subjects. We report in detail the nature and course of allergic reactions that occurred in 4 patients treated with FabAV. Cases of anaphylaxis, acute urticaria, angioedema, and delayed serum sickness are described. All reactions were easily treated with some combination of antihistamines, epinephrine, and steroids, with prompt resolution of signs and symptoms enabling further dosing of antivenom as required. Several of these cases may have resulted from batches of antivenom contaminated with Fc fragments. The overall incidence of immediate and delayed allergic reactions to this product appears so far to be lower than that reported with conventional whole-immunoglobulin G (IgG) antivenom, but postmarketing surveillance is warranted.
authors.affiliation: Division of Medical Toxicology, Department of Emergency Medicine, University of California San Diego Medical Center, and the California Poison Control System, San Diego Division, San Diego, CA, USA.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Clark
authors.forename: Patrick E
authors.initials: PE
authors.lastname: McKinney
authors.forename: Peter B
authors.initials: PB
authors.lastname: Chase
authors.forename: Frank G
authors.initials: FG
authors.lastname: Walter
mesh_terms: D000328:Adult; D000997:Antivenins / Q000009:adverse effects*; D005260:Female; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000209:etiology / Q000503:physiopathology*; D006969:Hypersensitivity, Immediate / Q000209:etiology / Q000503:physiopathology*; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D012909:Snake Bites / Q000188:drug therapy
chemical_list: D000997:Antivenins; C431183:Crotalidae Polyvalent immune Fab; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments