Comparison of Two Dose Regimens of Snake Antivenom for the Treatment of Snake Bites Envenoming in Nepal

Snake bites are considered as one of the major neglected public health issues of tropical areas. They occur chiefly in developing countries and mainly affect poor rural communities. Besides the inadequate supply, distribution and accessibility of antivenom, a major problem is the absence of standardized and adequate treatment protocol. There is a significant diversity in clinical practices, in particular concerning the dose of antivenom given. Additionally, antivenom is often given even in the absence of a clear indication for envenoming. Altogether, this leads to an incredible waste of a scarce and costly resource.

In Nepal there are gross disparities in the management and outcomes of snake bite envenoming. The country's national guidelines, issued in 2004, prescribe an initial antivenom dose that is 5 times less than the one advocated by most experts. The dosage recommended by the National guidelines is not based on scientific or clinical evidence, and currently, there is confusion about the adequate dose to be administered. Some physicians follow recommendations published by experts, others follow the National guidelines, but for most, dosage is arbitrary. These discrepancies directly impact on morbidity and mortality and lead to wastage of a costly treatment that few can afford.

The principal objective of the study is to establish unequivocally which dosage regimen is the most appropriate for the treatment of snake bite neurotoxic envenoming. It is a randomized, double-blind, clinical trial comparing high and low initial doses of snake polyvalent antivenom also known as Anti Snake Venom Serum (ASVS). 250 snake bite victims showing signs of neurotoxic envenoming will be enrolled over 2 years in three health centres of Southern Nepal. Each participant will initially receive either 2 vials or 10 vials of snake polyvalent antivenom. Mortality, the proportion of patients needing assisted respiration, and the percentage of patients who show worsening of neurotoxic signs and therefore require additional doses of antivenom will be compared in both arms. The kinetics of recovery and the total consumption of antivenom will also be compared. Finally, the incidence and severity of early and late adverse reactions to antivenom will be assessed. The economical impact of snake bite envenoming will also be determined by measuring direct and indirect costs to both health services and individual victims. Because they chiefly affect agricultural workers and children, snake bites have serious economic consequences, a fact that is frequently overlooked by national authorities.

Inclusion criteria

• History of snake bite; AND
• Age ≥ 5 years; AND
• Informed consent obtained; AND
• Showing one or more signs of neurotoxic envenoming

Exclusion criteria

• Subject unlikely to co-operate in the study
• Pregnant or breastfeeding women
• Patients presenting more than 24 hours after the bite
• Patients requiring ventilation support at the time of presentation
• Subjects with previous history of snake bite with envenoming
• Patients who already received antivenom before presenting to the study centre
• Patients with pre-existing neurological or muscular disorders
• Subjects with known history of allergy to horse proteins
• Patients with proven viper bites