PRETREATMENT WITH EPINEPHRINE TO PREVENT EARLY REACTIONS

Epinephrine is the only prophylactic treatment (pretreatment) that has been shown to effectively reduce the incidence of early adverse reactions (EARs) such as anaphylaxis.^{60,98,133–136} See Antivenom Reactions Algorithm.

1. DO NOT pretreat with steroids or antihistamines, as they not only have no benefit prior to a reaction but may reduce the efficacy of epinephrine as a pretreatment for EARs.^134,273

2. DO NOT administer test doses of antivenom to check for hypersensitivity.^60–63

Relative contraindications to epinephrine pretreatment include age > 70, hypertension, ischemic heart disease, history of stroke, suspected or confirmed intracranial hemorrhage. No absolute contraindications.

1. Pretreatment with epinephrine prior to antivenom administration is not indicated by default for all antivenoms, and is recommended only under the following circumstances:

a. Unstable snakebite patients with signs of shock.

b. Known history of atopy (asthma, eczema, etc.), equine hypersensitivity, or severe reactions to antivenom in the past.

c. Use of certain second or third line antivenom due to the high rate of serious EARs associated with these products.

2. Standard epinephrine pretreatment protocol:

a. Adult dose is 0.25 mg of 1:1000 epinephrine given by IM injection several minutes prior to antivenom administration.

b. Pediatric doses should be weight based at a dose of 0.01 mg/kg, up to 0.25 mg.^{60,134,135,137,138}

c. Alternatively, consider establishing two intravenous catheters (one for the antivenom and one for epinephrine) and preparing an epinephrine infusion that can be immediately initiated in the event an allergic reaction to the antivenom occurs.