Poison and Antidote Actions
A poison is a compound that produces a deleterious change on or in the body. There are a large number of known poisons, with a myriad of effects. Toxicity is a general term used to indicate adverse effects produced by poisons. These adverse effects can range from slight symptoms such as headaches or nausea, to severe symptoms such as coma, convulsions, and death.
The hallmark of a poison is that it changes some aspect of a body function, often the speed of a function. Examples of this include increased heart rate or sweating, or decreasing breath (sometimes to the point of death). A poison may have wide-ranging effects in the body, may damage only a particular region or organ, or may do both. An example of the latter is an insecticide called Parathion. It inactivates a particular enzyme that functions in communication between nerves. The enzyme is very widespread in the body, and thus many varied effects are seen.
Toxicity is based on the number of exposures to a poison and the time it takes for toxic symptoms to develop. Two common types are acute and chronic toxicity. Acute toxicity is due to short-term exposure and happens within a relatively short period of time, whereas chronic toxicity is due to long-term exposure and happens over a longer period.
Some poisons produce a mild reaction. Poison ivy, poison oak and poison sumac all contain a sticky sap comprised of a compound called toxicodendrol. For individuals who are allergic to the compound--more than half the population--a red, blistering rash called rhus dermatitis results upon contact with the plant. There are no antidotes per se, as the rash cannot be reversed. Antihistamines or drying agents such as calamine provide comfort and lessen the rash.
The toxins produced by bacteria are far more potent poisons than toxicodendrol. The effects of bacterial toxins are varied, ranging from the vomiting and diarrhea associated with toxins of Escherichia coli and Shigella, to the paralysis and death caused by the toxin produced by Clostidium botulinum. If detected early enough, relief is brought by the injection of an antitoxin, which neutralizes the toxin that has not yet bound to its target. This antidote is ineffective on toxin that has already bound to host tissue.
Plants are another source of poisons. Very many plants, if ingested, can cause vomiting, depression, tremors or convulsions, stomach pain, kidney or liver failure, coma, or death, to name just a few symptoms. The antidote depends on the type of plant. Treatment with ipecac to induce vomiting is a common antidote. But in some cases, an antidote does not exist. Then, stabilization of the patient and medical monitoring to prevent further damage is the course of action.
Compounds that are effective in one setting, or drugs that are therapeutic at certain concentrations, can be poisonous if used in an inappropriate way or at too high a concentration. As examples, bleach and other household detergents and cleaning agents are poisonous if ingested. And, while two aspirin are effective for treatment of a headache, 30 aspirin at one time are poisonous. The list of potential poisons is thus, numerous.
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