Incidence of immediate and delayed hypersensitivity to Centruroides antivenom

Study objective: To assess the incidence and course of immediate and delaye d hypersensitivity to Centruroides antivenom. Methods: We performed a 12-month prospective observation study, with teleph one follow-up, evaluating the incidence of anaphylaxis or anaphylactoid rea ctions and serum sickness after Centruroides antivenom administration. The setting for the study was a poison control center and tertiary care toxicol ogy treatment center. Participants included all patients who received Centr uroides antivenom, and no interventions were performed. Results: For immediate hypersensitivity reactions, 116 patients with grade III or IV envenomation received Centruroides antivenom; 77 of these patient s were younger than 13 years. Three patients completed the infusion despite development of rash. A fourth patient with a history of atopy and asthma r eceived epinephrine infusion and an inhaled beta-agonist for transient whee zing that quickly resolved; she was admitted for observation. Nine patients without hypersensitivity reactions were admitted for social reasons, for i nappropriate sedation from drugs used before antivenom, or to rule out aspi ration; all were discharged within 24 hours. The remaining 106 patients wer e discharged from the emergency department after resolution of symptoms. Th us 4 of 116 patients had immediate reactions. For patients with delayed rea ctions, 17 patients were lost to follow-up. Of 99 remaining patients, serum sickness developed in 61% (n=60), as defined by using liberal criteria. Se rum sickness responded to oral steroids, antihistamines, or both; mean dura tion of symptoms with medication was 2.8 days. Conclusion: Anaphylactic reactions are uncommon after Centruroides antiveno m infusion. Self-limited serum sickness that is easily controlled with cort icosteroids and antihistamines commonly follows the use of Centruroides ant ivenom.