POISON :In the context of
biology,
poisons are
substances that can cause disturbances to
organisms,[SUP]
[1][/SUP] usually by
chemical reaction or other
activity on the
molecular scale, when a sufficient quantity is absorbed by an organism. In
medicine (particularly veterinary) and in
zoology, a poison is often distinguished from a
toxin and a
venom. Toxins are poisons produced via some biological function in nature, and venoms are usually defined as biological toxins that are injected by a bite or sting to cause their effect, while other poisons are generally defined as substances which are absorbed through epithelial linings such as the skin or gut.
Some poisons are also toxins, usually referring to naturally produced substances, such as the
bacterial proteins that cause
tetanus and
botulism. A distinction between the two terms is not always observed, even among scientists.
Animal toxins that are delivered subcutaneously (e.g. by
sting or
bite) are also called
venom. In normal usage, a poisonous organism is one that is harmful to consume, but a venomous organism uses poison to defend itself while still alive. A single organism can be both venomous and poisonous.
The derivative forms "toxic" and "poisonous" are synonymous.
In nuclear
physics, a poison is a substance that obstructs or inhibits a nuclear reaction. For an example, see
nuclear poison.
Paracelsus, the father of
toxicology, once wrote: "Everything is poison, there is poison in everything. Only the dose makes a thing not a poison." The term "poison" is often used
colloquially to describe any harmful substance, particularly
corrosive substances,
carcinogens,
mutagens,
teratogens and harmful
pollutants, and to exaggerate the dangers of chemicals. The legal definition of "poison" is stricter. A medical condition of poisoning can also be caused by substances that are not legally required to carry the label "poison".
Environmentally hazardous substances are not necessarily poisons and vice versa. For example, food industry wastewater - which may contain milk or potato juice - can be hazardous to the ecosystems of streams and rivers by consuming oxygen and causing
eutrophication, but is nonhazardous to humans and not classified as a poison.Biological poisoning
Acute poisoning is exposure to a poison on one occasion or during a short period of time. Symptoms develop in close relation to the exposure. Absorption of a poison is necessary for systemic poisoning. In contrast, substances that destroy tissue but do not absorb, such as
lye, are classified as
corrosives rather than poisons. Furthermore, many common household medications are not labeled with skull and crossbones, although they can cause severe illness or even death. In the medical sense, poisoning can be caused by less dangerous substances than those receiving the legal classification of "poison".
Chronic poisoning is long-term repeated or continuous exposure to a poison where symptoms do not occur immediately or after each exposure. The patient gradually becomes ill, or becomes ill after a long latent period. Chronic poisoning most commonly occurs following exposure to poisons that
bioaccumulate, or are
biomagnified, such as
mercury and
lead.
Contact or absorption of poisons can cause rapid death or impairment. Agents that act on the
nervous system can paralyze in seconds or less, and include both biologically derived
neurotoxins and so-called
nerve gases, which may be synthesized for
warfare or industry.
Inhaled or ingested
cyanide, used as a method of
execution in
gas chambers, almost instantly starves the body of energy by
inhibiting the
enzymes in
mitochondria that make
ATP. Intravenous injection of an unnaturally high concentration of
potassium chloride, such as in the execution of prisoners in parts of the United States, quickly stops the
heart by eliminating the
cell potential necessary for
muscle contraction.
Most biocides, including
pesticides, are created to act as poisons to
target organisms, although acute or less observable chronic poisoning can also occur in non-target organism, including the
humans who apply the biocides and other
beneficial organisms. For example, the herbicide
2,4-D imitates the action of a plant hormone, to the effect that the lethal toxicity is specific to plants. Indeed, 2,4-D is not a poison, but classified as "harmful" (EU).
Many substances regarded as poisons are toxic only indirectly, by
toxication. An example is "wood alcohol" or
methanol, which is not poisonous itself, but is chemically converted to toxic
formaldehyde and
formic acid in the
liver. Many
drug molecules are made toxic in the liver, and the genetic variability of certain liver
enzymes makes the toxicity of many compounds differ between individuals.
The study of the symptoms, mechanisms, treatment and diagnosis of biological poisoning is known as
toxicology.
Exposure to radioactive substances can produce
radiation poisoning, an unrelated phenomenon.Initial management
- Initial management for all poisonings includes ensuring adequate cardiopulmonary function and providing treatment for any symptoms such as seizures, shock, and pain.
- Poisons that have been injected (e.g. from the sting of poisonous animals) can be treated by binding the affected body part with a pressure bandage and by placing the affected body part in hot water (with a temperature of 50°C). The pressure bandage makes sure the poison is not pumped troughout the body and the hot water breaks down the poison. This treatment however only works with poisons that are composed of protein-molecules.[SUP][5][/SUP]Decontamination
- [SUP]If the toxin was recently ingested, absorption of the substance may be able to be decreased through gastric decontamination. This may be achieved using [/SUP][SUP]activated charcoal[/SUP][SUP], [/SUP][SUP]gastric lavage[/SUP][SUP], [/SUP][SUP]whole bowel irrigation[/SUP][SUP], or [/SUP][SUP]nasogastric aspiration[/SUP][SUP]. Routine use of emetics ([/SUP][SUP]syrup of Ipecac[/SUP][SUP]), [/SUP][SUP]cathartics[/SUP][SUP] or laxatives are no longer recommended. [/SUP]
- [SUP]Activated charcoal[/SUP][SUP] is the treatment of choice to prevent absorption of the poison. It is usually administered when the patient is in the emergency room or by a trained emergency healthcare provider such as a Paramedic or EMT. However, charcoal is ineffective against [/SUP][SUP]metals[/SUP][SUP] such as [/SUP][SUP]sodium[/SUP][SUP], [/SUP][SUP]potassium[/SUP][SUP], and [/SUP][SUP]lithium[/SUP][SUP], and [/SUP][SUP]alcohols[/SUP][SUP] and [/SUP][SUP]glycols[/SUP][SUP]; it is also not recommended for ingestion of corrosive chemicals such as [/SUP][SUP]acids[/SUP][SUP] and [/SUP][SUP]alkalis[/SUP][SUP].[/SUP][SUP][6][/SUP]
- [SUP]Whole bowel irrigation[/SUP][SUP] cleanses the bowel, this is achieved by giving the patient large amounts of a [/SUP][SUP]polyethylene glycol[/SUP][SUP] solution. The osmotically balanced polyethylene glycol solution is not absorbed into the body, having the effect of flushing out the entire [/SUP][SUP]gastrointestinal tract[/SUP][SUP]. Its major uses are following ingestion of sustained release drugs, toxins that are not absorbed by activated charcoal (i.e. [/SUP][SUP]lithium[/SUP][SUP], [/SUP][SUP]iron[/SUP][SUP]), and for the removal of ingested packets of drugs ([/SUP][SUP]body packing[/SUP][SUP]/smuggling).[/SUP][SUP][7][/SUP]
- [SUP]Gastric lavage[/SUP][SUP], commonly known as a stomach pump, is the insertion of a tube into the stomach, followed by administration of water or saline down the tube. The liquid is then removed along with the contents of the stomach. Lavage has been used for many years as a common treatment for poisoned patients. However, a recent review of the procedure in poisonings suggests no benefit.[/SUP][SUP][8][/SUP][SUP] It is still sometimes used if it can be performed within 1 hour of ingestion and the exposure is potentially life threatening.[/SUP]
- [SUP]Nasogastric aspiration[/SUP][SUP] involves the placement of a tube via the nose down into the stomach, the stomach contents are then removed via suction. This procedure is mainly used for liquid ingestions where activated charcoal is ineffective, e.g. [/SUP][SUP]ethylene glycol poisoning[/SUP][SUP].[/SUP]
- [SUP]Emesis[/SUP][SUP] (i.e. induced by ipecac) is no longer recommended in poisoning situations, because vomiting is ineffective at removing poisons.[/SUP][SUP][9][/SUP]
- [SUP]Cathartics[/SUP][SUP] were postulated to decrease absorption by increasing the expulsion of the poison from the [/SUP][SUP]gastrointestinal tract[/SUP][SUP]. There are two types of cathartics used in poisoned patients; saline cathartics ([/SUP][SUP]sodium sulfate[/SUP][SUP], [/SUP][SUP]magnesium citrate[/SUP][SUP], [/SUP][SUP]magnesium sulfate[/SUP][SUP]) and saccharide cathartics ([/SUP][SUP]sorbitol[/SUP][SUP]). They do not appear to improve patient outcome and are no longer recommended.[/SUP][SUP][10][/SUP]AntidotesSome poisons have specific antidotes:
[TABLE="class: wikitable"]
[TR]
Poison/DrugAntidote[/TR]
[TR]
[TD]paracetamol (acetaminophen)[/TD]
[TD]N-acetylcysteine[/TD]
[/TR]
[TR]
[TD]vitamin K anticoagulants, e.g. warfarin[/TD]
[TD]vitamin K[/TD]
[/TR]
[TR]
[TD]opioids[/TD]
[TD]naloxone[/TD]
[/TR]
[TR]
[TD]Iron (and other heavy metals)[/TD]
[TD]desferrioxamine, Deferasirox or Deferiprone[/TD]
[/TR]
[TR]
[TD]benzodiazepines[/TD]
[TD]flumazenil[/TD]
[/TR]
[TR]
[TD]ethylene glycol[/TD]
[TD]ethanol or fomepizole, and thiamine[/TD]
[/TR]
[TR]
[TD]methanol[/TD]
[TD]ethanol or fomepizole, and folinic acid[/TD]
[/TR]
[TR]
[TD]Cyanide[/TD]
[TD]amyl nitrite, sodium nitrite and sodium thiosulfate[/TD]
[/TR]
[TR]
[TD]Organophosphates[/TD]
[TD]Atropine and Pralidoxime[/TD]
[/TR]
[TR]
[TD]Magnesium[/TD]
[TD]Calcium Gluconate[/TD]
[/TR]
[TR]
[TD]Calcium Channel Blockers (Verapamil, Diltiazem)[/TD]
[TD]Calcium Gluconate[/TD]
[/TR]
[TR]
[TD]Beta-Blockers (Propranolol, Sotalol)[/TD]
[TD]Calcium Gluconate and/or Glucagon[/TD]
[/TR]
[TR]
[TD]Isoniazid[/TD]
[TD]Pyridoxine[/TD]
[/TR]
[TR]
[TD]Atropine[/TD]
[TD]Physostigmine[/TD]
[/TR]
[TR]
[TD]Thallium[/TD]
[TD]Prussian blue[/TD]
[/TR]
[TR]
[TD]Hydrofluoric acid[/TD]
[TD]Calcium Gluconate[/TD]
[/TR]
[TR]
[TD]AnticholinergicsEnhanced excretion[/TD]
[TD]Cholinergics (and vice-versa)[/TD]
[/TR]
[/TABLE]