Abstract
Snake antivenoms are the only definitive management of snake envenoming. Parenteral administration of antivenom mitigates the toxic effects due to snake venom components. However, these benefits come with additional risk of antivenom reactions. The morbidity and mortality of antivenom reactions largely go unnoticed due to lack of awareness and many times these are wrongly attributed to effects of snake venoms. Depending upon the duration between antivenom administration and onset of clinical manifestations, World Health Organization (WHO) has classified these reactions into three types; namely i) early anaphylactic reactions: occur within 10-180 minutes after antivenom infusion, ii) pyrogenic (endotoxic) reactions: develop within 1-2 hours after initiation of treatment, and iii) late reactions: usually develop 1-12 (mean 7) days after treatment. The conjunctival or skin hypersensitivity tests are not only unreliable but can also be sensitizing to antivenom reactions, and hence, not recommended by WHO. The majority of early anaphylactic reactions are non-IgE mediated owing to anticomplementary activity of antivenom and few reactions are attributed to IgE mediated release of anaphylotoxins namely histamines, leukotriens etc. Contamination of antivenom with endotoxins during manufacturing process leads to development of pyrogenic reactions. Late antivenom reactions are the result of production of IgM or IgG antibodies in patients towards antivenom proteins, which ultimately cause formation of immune complexes. The deposition of these immune complexes throughout body leads to manifestations of late reactions. There should be a vigilant approach towards prediction and prevention of antivenom reactions for a better quality of health care.
Highlights
Snake envenoming and the associated morbidity and mortality is one of the important public health problems in rural tropical areas like Southeast Asia, sub-Saharan Africa, Latin America
As per World Health Organization (WHO) guidelines on the management of snake bites, it has been documented that usually more than 10% of patients who receive antivenom suffer from antivenom reactions [25]
The benefits of antivenom in managing snake envenomings come with additional risk of antivenom reactions
Summary
Snake envenoming and the associated morbidity and mortality is one of the important public health problems in rural tropical areas like Southeast Asia, sub-Saharan Africa, Latin America. The polyspecific antivenoms are produced by immunizing an animal with venoms of more than one species of snakes of high medical relevance to the concerned geographic area Another methods of production includes i) immunizing individual animals with venom of a single species and mixing the various hyper immune plasmas for fractionation and ii) mixing appropriate quantities of relevant purified antivenoms before formulation [7]. These polyspecific antivenoms should be promoted whenever feasible technically, as they offer clinical advantages like better usefulness than monospecific antivenoms. Screening production animals for adventitious agents IgG concentrations [(NH4)2SO4/NaSO4 precipitation] Enzyme digestion (pepsin ? F(ab’); papain ? Fab Caprylic acid stabilization Ion exchange (removes Fc) Affinity purification (concentrates venom-specific IgG) Pasteurisation (10 h at 60°C) Endotoxin exclusion (to not more than 0.5 u/kg/dose) Lyophilisation
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