Poison and Antidote Actions

A variety of chemical and biological compounds can damage tissues, organs, and organs systems of the body. Amphetamines , barbiturates , and botulinum toxin debilitate the nervous system, for example. Other toxins produced by bacteria such as Escherichia coli and Vibrio cholerae can damage the cells lining the intestinal tract. A particularly vicious strain of E. coli designated O157:H7 produces a toxin that can permanently disable the kidneys.

These and other poisons can become an important focus of a forensic examination that seeks to determine the cause of an illness or death.

A poison is a compound that produces a deleterious change on or in the body. Toxicity is a general term used to indicate adverse effects produced by poisons. As touched on above, 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 the change elicited in a body function. This change can involve the speed of a function. Examples of this can include increased heart rate, excessive sweating, and decreased (or completely stopped) breath.

The target of poisons vary widely. With some poisons only a particular region or organ may be damaged, while other poisons, such as a bacterial toxin that can circulate in the bloodstream, may have more general effects. Another 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.

These differing manifestations of poisoning mean that a forensic investigator must be familiar with the spectrum of possible poison hazards and their toxic effects.

Toxicity is based on the number of exposures to a poison and the time it takes for toxic symptoms to develop. Acute toxicity is due to short-term exposure and happens within a relatively short period of time. 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 comprising 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 can be far more potent poisons than toxicodendrol. The effects of bacterial toxins are varied, ranging from the vomiting and diarrhea associated with toxins of E. 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. 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.

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. Barbiturates taken in a prescribed quantity can help calm a person, but an accidental or deliberate overdose of the drugs can kill. And, while two aspirin are effective for treatment of a headache, 30 aspirin at one time are poisonous.

see also Amphetamines; Barbiturates; Bioterrorism; Botulinum toxin; Chemical and biological detection technologies; Food poisoning; Nervous system overview; Toxins.