|Synonyms||Snake antivenin, snake antivenene, snake venom antiserum, antivenom immunoglobulin|
It is a biological product that typically consists of venom neutralizing antibodies derived from a host animal, such as a horse or sheep. The host animal is hyperimmunized to one or more snake venoms, a process which creates an immunological response that produces large numbers of neutralizing antibodies against various components (toxins) of the venom. The antibodies are then collected from the host animal, and further processed into snake antivenom for the treatment of envenomation.
They are on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.
Antivenoms are typically produced using a donor animal, such as a horse or sheep. The donor animal is hyperimmunized with non-lethal doses of one or more venoms to produce a neutralizing antibody response. Then, at certain intervals, the blood from the donor animal is collected and neutralizing antibodies are purified from the blood to produce an antivenom.
- Human Medicine: In the United States, antivenom production and distribution is regulated by the Food and Drug Administration.
- Veterinary Medicine: In the United States, antivenom production and distribution is regulated by the United States Department of Agriculture's Center for Veterinary Biologics.
Monovalent vs. polyvalent
Snake antivenom can be classified by which antigens (venoms) were used in the production process. If the hyperimmunizing venom is obtained from a single species, then it is considered a monovalent antivenom. If the antivenom contains neutralizing antibodies raised against two or more species of snakes, then the composition is considered polyvalent.
Compositions of the antivenom can be classified as whole IgG, or fragments of IgG. Whole antibody products consist of the entire antibody molecule, often immunoglobulin G (IgG), whereas antibody fragments are derived by digesting the whole IgG into Fab (monomeric binding) or F(ab')2 (dimeric binding). The fragment antigen binding, or Fab, is the selective antigen binding region. An antibody, such as IgG, can be digested by papain to produce three fragments: two Fab fragments and one Fc fragment. An antibody can also be digested by pepsin to produce two fragments: a F(ab')2 fragment and a pFc' fragment. The fragment antigen-binding (Fab fragment) is a region on an antibody that binds to antigens, such as venoms. The molecular size of Fab is approximately 50kDa, making it smaller than F(ab')2 which is approximately 110kDa. These size differences greatly affect the tissue distribution and rates of elimination.
Cross neutralization properties
Antivenoms may also have some cross protection against a variety of venoms from snakes within the same family or genera. For instance, Antivipmyn (Instituto Bioclon) is made from the venoms of Crotalus durissus and Bothrops asper. Antivipmyn has been shown to cross neutralize the venoms from all North American pit vipers. Cross neutralization affords antivenom manufacturers the ability to hyperimmunize with fewer venom types to produce geographically suitable antivenoms.
Families of venomous snakes
Over 600 species are known to be venomous—about a quarter of all snake species. The following table lists some major species.
|Atractaspididae (atractaspidids)||Burrowing asps, mole vipers, stiletto snakes.|
|Colubridae (colubrids)||Most are harmless, but others have toxic saliva and at least five species, including the boomslang (Dispholidus typus), have caused human fatalities.|
|Elapidae (elapids)||Sea snakes, Taipans, Brown snakes, Coral snakes, Kraits, King Cobra, Mambas, Cobras.|
|Viperidae (viperids)||True vipers and pit vipers, including rattlesnakes and copperheads and cottonmouths.|
|Polyvalent snake antivenom||South American Rattlesnake Crotalus durissus and fer-de-lance Bothrops asper||Mexico (Instituto Bioclon)|
|Polyvalent snake antivenom||South American Rattlesnake Crotalus durissus and fer-de-lance Bothrops asper||South America|
|Polyvalent snake antivenom||Saw-scaled Viper Echis carinatus, Russell's Viper Daboia russelli, Spectacled Cobra Naja naja, Common Krait Bungarus caeruleus||India|
|Death adder antivenom||Death adder||Australia|
|Black snake antivenom||Pseudechis spp.||Australia|
|Tiger snake antivenom||Australian copperheads, Tiger snakes, Pseudechis spp., Rough scaled snake||Australia|
|Brown snake antivenom||Brown snakes||Australia|
|Polyvalent snake antivenom||Many Australian snakes||Australia|
|Sea snake antivenom||Sea snakes||Australia|
|Vipera tab||Vipera spp.||UK|
|Polyvalent crotalid antivenin (CroFab - Crotalidae Polyvalent Immune Fab (Ovine))||North American pit vipers (all rattlesnakes, copperheads, and cottonmouths)||North America|
|Soro antibotropicocrotalico||Pit vipers and rattlesnakes||Brazil|
|SAIMR polyvalent antivenom||Mambas, Cobras, Rinkhalses, Puff adders (Unsuitable small adders: B. worthingtoni, B. atropos, B. caudalis, B. cornuta, B. heraldica, B. inornata, B. peringueyi, B. schneideri, B. xeropaga)||South Africa|
|SAIMR echis antivenom||Saw-scaled vipers||South Africa|
|SAIMR Boomslang antivenom||Boomslang||South Africa|
|Panamerican serum||Coral snakes||Costa Rica|
|Anticoral||Coral snakes||Costa Rica|
|Anti-mipartitus antivenom||Coral snakes||Costa Rica|
|Anticoral monovalent||Coral snakes||Costa Rica|
|West Africa polyvalent (EchiTAb-plus-ICP)||Carpet vipers, Puff adders, Black-necked spitting cobras||Costa Rica|
- WHO Model Formulary 2008 (PDF). World Health Organization. 2009. p. X. ISBN 9789241547659. Retrieved 8 January 2017.
- "WHO Model List of Essential Medicines (19th List)" (PDF). World Health Organization. April 2015. Retrieved 8 December 2016.
- EE Sanchez, et al. The efficacy of two antivenoms against the venom of North American snakes. Toxicon 41 (2003) 357–365.
- Spawls, S; Branch B (1995). The Dangerous Snakes of Africa. Ralph Curtis Books. Dubai: Oriental Press. p. 192. ISBN 0-88359-029-8.