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Poison

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For other uses, see Poison (disambiguation).
EU standard toxic symbol, as defined by Directive 67/548/EEC.

In the context of biology, poisons are substances that can cause damage, illness, or death to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. Legally and in hazardous chemical labelling, poisons are especially toxic substances; less toxic substances are labelled "harmful", "irritant", or not labelled at all.

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 biologic 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.

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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.

Initial medical management

Decontamination

  • If the toxin was recently ingested, absorption of the substance may be able to be decreased through gastric decontamination. This may be achieved using activated charcoal, gastric lavage, whole bowel irrigation, or nasogastric aspiration. Routine use of emetics (syrup of Ipecac) and cathartics are no longer 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. Its 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).[1]
    • Gastric lavage, 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.[2] It is still sometimes used if it can be performed within 1 h of ingestion and the exposure is potentially life threatening.
    • Nasogastric aspiration 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, i.e. ethylene glycol.
    • Emesis (i.e. induced by ipecac) is no longer recommended in poisoning situations.[3]
    • 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.[4]

Antidotes

Some poisons have specific antidotes:

Poison/Drug Antidote
paracetamol (acetaminophen) N-acetylcysteine
vitamin K anticoagulants, e.g. warfarin vitamin K
opioids naloxone
iron (and other heavy metals) desferrioxamine, Deferasirox or Deferiprone
benzodiazepines flumazenil
ethylene glycol ethanol, fomepizole or Thiamine
methanol ethanol or fomepizole
cyanide amyl nitrite, sodium nitrite & sodium thiosulfate
Organophosphates Atropine & Pralidoxime
Magnesium Calcium Gluconate
Calcium Channel Blockers (Verapamil, Diltiazem) Calcium Gluconate
Beta-Blockers (Propranolol, Sotalol) Calcium Gluconate and/or Glucagon
Isoniazid Pyridoxine
Atropine Phisostigmin

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

(T36) Poisoning by systemic antibiotics

(T37) Poisoning by other systemic anti-infectives and antiparasitics

(T38) Poisoning by hormones and their synthetic substitutes and antagonists, not elsewhere classified

(T39) Poisoning by nonopiod analgesics, antipyretics and antirheumatics

(T40) Poisoning by narcotics and psychodysleptics (hallucinogens)

(T41) Poisoning by anaesthetics and therapeutic gases

(T42) Poisoning by antiepileptic, sedative-hypnotic and antiparkinsonism drugs

(T43) Poisoning by psychotropic drugs, not elsewhere classified

(T44) 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

(T45) Poisoning by primarily systemic and haematological agents, not elsewhere classified

(T46) Poisoning by agents primarily affecting the cardiovascular system

(T47) Poisoning by agents primarily affecting the gastrointestinal system

(T48) Poisoning by agents primarily acting on smooth and skeletal muscles and the respiratory system

(T49) Poisoning by topical agents primarily affecting skin and mucous membrane and by ophthalmological, otorhinolaryngological and dental drugs

(T50) Poisoning by diuretics and other unspecified drugs, medicaments and biological substances

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

(T51) Toxic effect of alcohol

(T52) Toxic effect of organic solvents

(T53) Toxic effect of halogen derivatives of aliphatic and aromatic hydrocarbons

(T54) 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.

(T55) Toxic effect of soaps and detergents

(T56) Toxic effect of metals A common trait shared by toxic metals is the chronic nature of their toxicity (a notable exception would be bismuth, which is considered entirely non-toxic). Low levels of toxic metal salts ingested over time accumulate in the body until toxic levels are reached. Toxic metals are often inaccurately referred to as "heavy metals", although not all heavy metals are necessarily harmful and not all toxic metals are heavy metals.

Toxic 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:

(T57) Toxic effect of other inorganic substances

Reducing agents

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

(T58) Toxic effect of carbon monoxide

(T59) 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

(T60) Toxic effect of pesticides

(T61) Toxic effect of noxious substances eaten as seafood

(T62) Toxic effect of other noxious substances eaten as food

(T63) Toxic effect of venomous animals

(T64) Toxic effect of aflatoxin and other mycotoxin food contaminants

(T65) Toxic effect of other and unspecified substances

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

References

  1. ^ "Position paper: whole bowel irrigation". J Toxicol Clin Toxicol. 42 (6): 843–54. 2004. PMID 15533024.
  2. ^ Vale JA, Kulig K; American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. (2004). "Position paper: gastric lavage". J Toxicol Clin Toxicol. 42 (7): 933–43. PMID 15641639.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ "Position paper: Ipecac syrup". J Toxicol Clin Toxicol. 42 (2): 133–43. 2004. PMID 15214617.
  4. ^ "Position paper: cathartics". J Toxicol Clin Toxicol. 42 (3): 243–53. 2004. PMID 15362590.

See also

External links

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