A medical classification of venom activities is based on specific clinical
effects and a single venom toxin may have activities in several different areas
(ie some PLA2 toxins have both presynaptic neurotoxic and myotoxic activity).
It is also important to consider the way the different activities may affect
timing of onset of clinical effects.
Venom Toxicodynamics
In recent years it has been possible to measure venom or individual toxins over
time in both experimental animals and human snakebite victims. Though this has
so far only been performed for a very limited range of species, there is a greater
understanding of the toxicodynamics of envenoming . In most cases, venom is
injected fairly superficially, usually subcutaneously. Locally acting toxins
causing tissue injury will already be at their target site, so will commence
exerting their clinical effects immediately. A significant proportion of the
venom, in some species perhaps most venom, will not be absorbed directly into
the circulation. Instead it will be transported first via the lymphatic system,
entering the circulation via the thoracic duct. This helps explain the common
clinical finding of enlarged or tender lymph nodes draining the bite area and
also the high concentration of venom in these nodes at autopsy. Transport via
the lymphatic system may be rapid or sometimes delayed and there is a potential
for sequestration of venom locally, with prolonged release over hours or days.
Once in the circulation, those components affecting haemostasis or acting as
haemorrhagins will have reached their target site and will quickly exert their
effect. Similarly, nephrotoxins will quickly damage the kidneys. However, those
toxins seeking extravascular targets, particularly the neurotoxins and myotoxins,
will need to exit the circulation in sufficient concentration to exert their
effect clinically, thus these toxins are most likely to have a delayed onset
of clinically detectable actions. Some venoms are quickly cleared from the circulation,
but others remain detectable for days or even weeks without antivenom therapy.
Knowledge of such variations is clearly relevant in determining antivenom therapy.
Bite Site - local effects
Intravascular Compartment
Extravascular Compartment
Necrotoxins
Haemostatic System Toxins
Haemorrhagins
Nephrotoxins
Neurotoxins
Myotoxins
Cardiotoxins
Broad medical classification of snake venom activities.
IMPORTANT INFORMATION FOR ALL SITE USERS
: The principle aim of this site is to provide
information useful to improving outcomes for humans suffering from envenoming or poisoning by
animals, plants or mushrooms. We make a reasonable attempt to verify accuracy of information
listed on this site. However, we cannot access every published paper of potential relevance,
either because they are not available to us or are in a language we cannot translate internally.
Equally, we cannot list knowledge which is not yet reported or known. It should not be assumed
that humankind currently knows all there is to know about any species, even for common species.
Further, we cannot control how users will interpret the information provided on this site. We
therefore do not accept legal responsibility for use of the information provided and we require
that all users use information from this site at their own risk.
The following should also be noted when reading information contained within the databases on this website: italics for scientific nomenclature cannot be displayed, and superscripting and subscripting is absent in some instances.
Photos downloaded from Wikimedia Commons or other website are licensed for use under the Creative Commons Attribution-Share Alike 2.0 Generic license (CC BY-SA 2.0), 2.5 Generic license (CC BY-SA 2.5) or 3.0 Unported license (CC BY-SA 3.0), or the Attribution-NonCommerical-ShareAlike 3.0 Unported license (CC BY-NC-SA 3.0), or the Attribution-Share Alike 4.0 International license (CC BY-SA 4.0), or the GNU General Public License (GPL3.0), or in the Public Domain (PD), as shown in the caption to the image displayed on www.toxinology.com.