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In the context of biology, poisons are substances that can cause injury, illness, or death to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is present.

In medicine (particularly veterinary) and in zoology, a poison is often distinguished from a venom. Venoms are usually defined as biologic toxins that are injected to cause their effect, while poisons are generally defined as toxins which are absorbed through epithelial linings such as the skin or gut.

Terminology

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.

Within chemistry and physics, a poison is a substance that obstructs or inhibits a reaction, for example by binding to a catalyst.

Lay use

The phrase "poison" is often used colloquially to describe any harmful substance:

Warning symbols

Poisons have been known to be symbolized by the skull and crossbones (shown beside), although since this attracts children (being linked to pirates) it is gradually being replaced by Mr. Yuk in the United States. In the United Kingdom and some parts of Europe, irritant poisons are symbolised by a large "X" on an orange background.

Uses of poison

Deliberate application of poison has throughout the ages been used as method of assassination, murder, suicide and execution.

As a method of execution, the poison can be administered as ingested, as the ancient Athenians did (see Socrates), breathed, such as carbon monoxide or hydrogen cyanide (see gas chamber) or intravenously (see lethal injection). Many non-English languages describe lethal injection with their corresponding words for "poison shot".

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.

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 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 as used as method of execution on US 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 (but not all) 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 pesticides and other beneficial organisms.

Many substances regarded as poisons are toxic only indirectly. 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.

Poisoning in humans

Children

  • Poisoning is the fourth most common cause of accidents in children.
  • Children less than 5 years of age and adolescent are prone to poisoning.
  • Accidental ingestions are most common in children less than 5 years old.
  • 90% of all poisonings occur at home, the most common site being the kitchen and the bathroom.
  • Unintentional poisonings occur most frequently when routines are disrupted, for example moving and vacations.
  • Child safety caps have helped decrease the number of poisonings; however, they are not 100% effective and should not give a false sense of security.
  • All potential poisons should be properly labeled, stored out of reach of children, and locked.
  • Medications should not be taken in front of small children or called "candy" (or "sweets" for non Americans).
  • Adolescent ingestions are more typically a result of suicidal attempts or experimentation with illicit drugs.
  • Parents should receive anticipatory guidance regarding poisonings and should have the number to reach their local poison control center available, in the USA the phone number is 1-800-222-1222. Poison control centers are free, 24 hours, and confidential.

Poisoning management

  • Poison Control Centers (In the US reachable at 1-800-222-1222 at all hours) provide immediate, free, and expert treatment advice and assistance over the telephone in case of suspected exposure to poisons or toxic substances.

General first aid

  • If the poison is an inhalant, remove the patient from the area and to fresh air.
  • If the poisoning is affecting the skin, remove the clothing and wash the skin thoroughly unless a dry powder is the cause of the poisoning.
  • If the poison is in the eye, flush the eye thoroughly for at least 15 minutes.
  • Following ingestion, ensure the person remains calm, do not induce vomiting, small fluids are recommended for corrosive substances (e.g. household cleaners).
  • Following these measures a poison control center can be contacted for advice on what to do next.

Initial medical management

Decontamination

  • The goal of gastric decontamination is to prevent absorption of the toxin. This may be achieved using activated charcoal, whole bowel irrigation, or nasogastric aspiration. Gastric lavage, cathartics, emesis, or Ipecac are no longer routinely recommended.
    • Activated charcoal is the treatment of choice to prevent absorption of the poison. It is usually administered when the patient is in the emergency room. However, charcoal is ineffective against metals, Na, K, alcohols, glycols, acids, and alkalis.
    • Whole bowel irrigation cleanses the bowel, this is achieved by giving the patient large amounts of a polyethylene glycol solution. The osmotically balanced polyethylene glycol solution is not absorbed into the body, having the effect of flushing out the entire gastrointestinal tract. It major uses are following ingestion of sustained release drugs, toxins that are not absorbed by activated charcoal (i.e. lithium, iron), and for the removal of ingested packets of drugs (body packing/smuggling).
    • Nasogastric aspiration involves the placement of a tube via the nose down into the stomach, the stomach contents are then removed via suction. This proceedure is mainly used for liquid ingestions where activated charcoal is ineffective, i.e. ethylene glycol.
    • Gastric lavage, commonly know as a stomach pump, is the insertion of a tube through the mouth down into the stomach, followed by administration of water or saline down the tube, the liquid is then removed again, having the overall effect of removing the contents of the stomach. Lavage has been used for many years as an initial treatment for poisoned patients, however, a recent review of the proceedure for poison ingestions suggested lavage should no longer be employed routinely, if ever, in the management of poisoned patients. It is still sometimes performed if it can be performed within 1 h of ingestion and the dose is potentially life threatening.
    • Emesis (i.e. induced by ipecac) is no longer recommended in poisoning situations.
    • Cathartics were postulated to decrease absorption by increasing the expulsion of the poison from the gastrointestinal tract. There are two types of cathartics used in poisoned patients; saline cathartics (sodium sulfate, magnesium citrate, magnesium sulfate) and saccharide cathartics (sorbitol). They do not appear to improve patient outcome and are no longer recommended.

Antidotes

Enhanced excretion

Further treatment

  • In the majority of poisonings the mainstay of management is providing supportive care for the patient, i.e. treating the symptoms rather than the poison.

Types of poisons

The majority of this section is sorted by ICD-10 code, which classifies poisons based upon the nature of the poison itself. However, it is also possible to classify poisons based upon the effect the poison has (for example, "Metabolic poisons" such as Antimycin, Malonate, and 2,4-Dinitrophenol act by adversely disrupting the normal metabolism of an organism.)

(T36-T50) Poisoning by drugs, medicaments and biological substances

() Poisoning by systemic antibiotics

() Poisoning by other systemic anti-infectives and antiparasitics

() Poisoning by hormones and their synthetic substitutes and antagonists, not elsewhere classified

() Poisoning by nonopiod analgesics, antipyretics and antirheumatics

() Poisoning by narcotics and psychodysleptics (hallucinogens)

() Poisoning by anaesthetics and therapeutic gases

() Poisoning by antiepileptic, sedative-hypnotic and antiparkinsonism drugs

() Poisoning by psychotropic drugs, not elsewhere classified

() Poisoning by drugs primarily affecting the autonomic nervous system | Neurotoxins interfere with nervous system functions and often lead to near-instant paralysis followed by rapid death. They include most spider and snake venoms, as well as many modern chemical weapons. One class of toxins of interest to neurochemical researchers are the various cone snail toxins known as conotoxins.

Anticholinesterases (T44.0)

Acetylcholine antagonists

Cell membrane disrupters Others

  • Nicotine - not strictly a neurotoxin, but capable in large doses of causing heart attack

() Poisoning by primarily systemic and haematological agents, not elsewhere classified

() Poisoning by agents primarily affecting the cardiovascular system

() Poisoning by agents primarily affecting the gastrointestinal system

() Poisoning by agents primarily acting on smooth and skeletal muscles and the respiratory system

() Poisoning by topical agents primarily affecting skin and mucous membrane and by ophthalmological, otorhinolaryngological and dental drugs

() Poisoning by diuretics and other unspecified drugs, medicaments and biological substances

(T51-T65) Toxic effects of substances chiefly nonmedicinal as to source

() Toxic effect of alcohol

() Toxic effect of organic solvents

() Toxic effect of halogen derivatives of aliphatic and aromatic hydrocarbons

() Toxic effect of corrosive substances Corrosives mechanically damage biological systems on contact. Both the sensation and injury caused by contact with a corrosive resembles a burn injury.

  • Acids and bases, corrosives
    • Various light metal oxides, hydroxides, superoxides
    • Bleach, some pool chemicals, other hypochlorates (acidic and oxydizing effect)
    • Hydrofluoric acid

Acids (T54.2) Strong inorganic acids, such as concentrated sulfuric acid, nitric acid or hydrochloric acid, destroy any biological tissue with which they come in contact within seconds.

Bases (T54.3) Strong inorganic bases, such as lye, gradually dissolve skin on contact but can cause serious damage to eyes or mucous membranes much more rapidly. Ammonia is a far weaker base than lye, but has the distinction of being a gas and thus may more easily come into contact with the sensitive mucous membranes of the respiratory system. Quicklime, which has household uses, is a particularly common cause of poisoning. Some of the light metals, if handled carelessly, can not only cause thermal burns, but also produce very strongly basic solutions in sweat.

() Toxic effect of soaps and detergents

() Toxic effect of metals A common trait shared by heavy metals is the chronic nature of their toxicity (a notable exception would be bismuth, which is considered entirely non-toxic). Low levels of heavy metal salts ingested over time accumulate in the body until toxic levels are reached.

Heavy metals are generally far more toxic when ingested in the form of soluble salts than in elemental form. For example, metallic mercury passes through the human digestive tract without interaction and is commonly used in dental fillings—even though mercury salts and inhaled mercury vapor are highly toxic.

Examples:

() Toxic effect of other inorganic substances

Reducing agents

  • (T57.1) The most notable substance in this class is phosphorus.

() Toxic effect of carbon monoxide

() Toxic effect of other gases, fumes and vapours

Oxidizers Poisons of this class are generally not very harmful to higher life forms such as humans (for whom the outer layer of cells are more or less disposable), but lethal to microorganisms such as bacteria. Typical examples are ozone and chlorine (T59.4), either of which is added to nearly every municipal water supply in order to kill any harmful microorganisms present.

All halogens are strong oxidizing agents, fluorine (T59.5) being the strongest of all.

See also: Free radical

() Toxic effect of pesticides

() Toxic effect of noxious substances eaten as seafood

() Toxic effect of other noxious substances eaten as food

() Toxic effect of venomous animals

() Toxic effect of aflatoxin and other mycotoxin food contaminants

() Toxic effect of other and unspecified substances

  • (T65.0) Cyanide is a metabolic poison that bonds with an enzyme involved in ATP production.

References

See also

External links

Execution methods | Toxicology

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This article is licensed under the GNU Free Documentation License. It uses material from the "Poison".

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