Severe Adverse Drug Reaction Following Crotalidae Polyvalent Immune Fab (Ovine) Administration for Copperhead Snakebite

Objective: To present the case of a severe anaphylactic/anaphylactoid reaction to Crotalidae Polyvalent Immune Fab (Ovine) in a patient bitten by a copperhead snake. Case Summary: A 68-year-old man presented with progressive envenomation after receiving a copperhead snakebite on each hand. Crotalinae Fab antivenom was administered. While the initial and only dose was partially infusing, the patient developed an adverse drug reaction (ADR) of urticaria and hypotension, which resolved with cessation of the infusion, recurred with resumption of the infusion, and ultimately was completed with supportive care. An additional episode of hypotension, urticaria, and angioedema occurred shortly after antivenom therapy completion. Epinephrine was administered, resolving the reaction with complete patient recovery. The event received a Naranjo score of 10, indicating a definite ADR. Discussion: Treating copperhead snakebites with antivenom is a matter of debate. Concern over adverse events and cost induce some physicians to manage copperhead bites without antivenom because they are generally milder in severity. Conclusion: As demonstrated in this case, severe ADR can occur with Crotalinae Fab antivenom, and its efficacy for copperhead envenoming needs to be better established via placebo-controlled, randomized trials.