Are there any adverse effects of using antivenom or antibodies more than once for a snake bite?

Answer 1

Patients with a history of reactions to equine antiserum suffer an increased incidence and severity of reactions when given equine antivenom. Atopic subjects have no increased risk of reactions, but if they develop a reaction it is likely to be severe. In such cases, reactions may be prevented or ameliorated by pretreatment with subcutaneous adrenaline, antihistamine and hydrocortisone, or by continuous intravenous infusion of adrenaline during antivenom administration. Rapid desensitization is not recommended.

Early (anaphylactic) reactions develop within 10 to 180 minutes of starting antivenom in 3 to 84% of patients. The incidence increases with dose and decreases when more highly refined antivenom is used and administration is by intramuscular rather than intravenous injection. The symptoms are itching, urticaria, cough, nausea, vomiting, other manifestations of autonomic nervous system stimulation, fever, tachycardia, bronchospasm and shock. Very few of these reactions can be attributed to acquired Type I IgE-mediated hypersensitivity.


· Pyrogenic reactions result from contamination of the antivenom with endotoxins. Fever, rigors, vasodilatation and a fall in blood pressure develop one to two hours after treatment. In children, febrile convulsions may be precipitated.


· Late reactions of serum sickness (immune complex) type may develop 5 to 24 (mean 7) days after antivenom. The incidence of those reactions and the speed of their development increases with the dose of antivenom. Clinical features include fever, itching, urticaria, arthralgia (including the temporomandibular joint), lymphadenopathy, periarticular swellings, mononeuritis multiplex, albuminuria and, rarely, encephalopathy.