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Doses and effects
The effect of a substance depends not so much on its absolute quantity, but on its concentration in the body, which depends mostly on the absorbed dose. It is commonly accepted the doses to be measured as a quantity of the absorbed substance, which is related to a unit of a live weight – for example mg/kg.
Each physiologically active substance has basic effects, i.e. desired and side effect. Very often the dose, used for achievement of the desired effect, is quite similar to the dose, which causes some of the secondary effects. Practically death could also be added to the group of the incidental effects, because it is usually a result of one of them, which is carried to excess; that is why those, who like opium, most often die because their breathing ceases; cocaine addicts usually die from a heart attack.
The effective dose, ED-50, is the dose, in which among 50% from the animals and people for research, a certain effect is observed; each of the effects of a certain mean has its ED-50. The mortal dose LD-50 corresponds to the death of 50% of the animals and people for research. When we talk about toxicity of a particular substance, we, most often, mean its capability to cause death and then its toxicity is measured in LD.
Under real conditions the drug’s toxicity is determined by the toxicity of all the other substances, which can be found in it, and practically the toxicity of these matters is considerably greater than the one of the pure narcotic. Most often the street drugs are so impure that their use reminds more of a game of Russian roulette. It is thought that one of the possible reasons for death, among those, who prefer opium, is poisoning with quinine and barbiturates, which the drug contains.