POISONS

From Big Medical Encyclopedia

poisons — substances, to-rye can cause poisonings.

Nek-ry industrial substances, natural toxins, chemical warfare agents, etc., and also the pharmaceuticals included in the list A of the State pharmacopeia belong to poisons. However reckoning of these or those substances to poisons is very relative as poisoning can come at receipt in an organism moderately of toxics in rather high dose. Substances, danger can be also carried to poisons to-rykh is defined not by a lethal dose or concentration, and the dose causing selective toxic effect, napr, psychotomimetic, emetic, etc. At the same time it is wrong to rank to I. low-toxic and the more so almost harmless substances though they under special conditions (e.g., one-time reception of 300 — 400 g of sodium chloride) can cause a serious poisoning.

Reference to I. toxicants of an endogenous origin — biologically active agents (see), hormones (see), mediators (see), etc. — it is justified only when these substances are entered into an organism from the outside, i.e. are exogenous.

Interaction I. with live organisms it is shown at all evolutionary levels, beginning from the inferior plants and finishing the highest animals. A number of poisons selectively affects various representatives of a plant and animal life that allows to emit substances, poisonous is preferential for plants (herbicides), bacteria (bactericides), insects (insecticides) etc.

Standard classification I. no. It is possible to classify them by origin and belongings to certain classes of chemical connections. Besides, I. divide into certain groups depending on the sphere of their preferential use (household, industrial, etc.). Also classifications I are offered., the estimates of their toxic action based on various principles — biochemical, pathophysiological and clinical. In a basis of biochemical (patokhimichesky) classification I. the type of their interaction with biochemical substrates is put. By this principle among I. emit, e.g., the substances denaturing proteins (acids, alkalis), the substances which are inhibitors of enzymes (organophosphorous connections), the substances blocking functional groups of proteins and coenzymes (cyanides, hydrogen sulfide), etc. According to patofiziol. the principle among I. emit so-called hypoxemic substances, to-rye, in turn, divide into a number of groups depending on type of the caused hypoxia (see): I., causing a fabric hypoxia (cyanides, etc.); I., causing a ge-michesky hypoxia (a methemoglobin - the forming connections, carbon monoxide, etc.); I., causing a circulator hypoxia (compounds of arsenic, a dichloroethane, etc.). In a basis wedge, classifications I. the syndromic principle of assessment of the poisonings caused by them is put. According to this principle Ya. divide on convulsive, neuroparalytic, narcotic, etc. On an organospetsifichnost I. can be hepatotoxic, nefrotoksiches - Kimi, neurotoxic etc. Proceeding from ideas of mechanisms of the damaging action I. at the cellular and subcellular levels, it is possible to allocate I. preferential cytotoxic and membranotoksichesky action.

For manifestation of toxic effect physical condition I matters., its water solubility and lipids, and also way of receipt to an organism.

Interaction I. decides on an organism their toksikokinetiky and toksikodinamiky. Distribution I. in an organism depends on three major factors: space (ways of receipt and distribution), temporary (speed of receipt in an organism, destruction and allocation) and concentration (concentration I. or its toxic metabolites in blood and in bodies).

At impact on an organism I. can have local and resorptive action. The last is shown generally by defeat of certain bodies and systems. For nek-ry I. existence of the eclipse (latent) period of action, duration to-rogo generally is characteristic I am defined by the speed of penetration. in an organism or intensity of formation of toxic metabolites.

Allocate primary action I. (interaction with biol. targets — enzymes, receptors, membranes), a cut plays a role of a releaser patol. process, and the systemic action which is expressed disturbances of functions of appropriate authorities and fiziol. systems and defining a clinical picture of poisoning.

I. cause three types patol. shifts: primary shifts, svya

zonal with specific action I.; adaptive and compensatory reactions of various intensity; development wedge, pictures of poisoning (symptom complex of poisoning, characteristic of this poison).

On action I. to a certain extent can render - influence environmental factors (air temperature, humidity, atmospheric pressure, etc.) and degree of order of an organism to it. At repeated receptions nek-ry I. their action can change both towards increase in toxicity (cumulation), and towards its reduction (tolerance). The last has relative character since eventually leads to decrease in the general resistance of an organism. Besides, at repeated introductions the allergy to poisons which is directly not connected with its toxicity can sometimes develop.

Treatment of poisonings is based on the following principles: the accelerated removal I. from an organism (methods of an active detoxication), urgent use of means of antidotal and pathogenetic therapy (intensive care), a symptomatic treatment and the prevention of the remote effects of poisonings (see).

Assessment of severity of poisoning at the victims and a research of corpses of the dead from poisoning make a subject of forensic medical examination (see Poisonings, poisonings in the medicolegal relation).

Bibliography: Luzhniki E. A. Kli

nichesky toxicology, M., 1982; M of au g about sh. Acute poisonings, the lane from Romanians., Bucharest, 1984; Acute management at acute poisonings, under the editorship of S. N. Golikov, page 5, M., 1977; Toxicology, ed. by L. J, Casarett a. J. Doull, N. Y., 1975. C.H. Golikov.

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