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Absorption, Distribution, Metabolism and Excretion

The effect of a particular substance depends on its concentration in the brain; it is determined by the way this substance enters the organism, by the speed of penetration into the brain and by the speed of its dissociation and excretion. A substance can get into the organism in different ways; almost all of them are used in one or another degree, and the way of absorption affects considerably the time, for which it penetrates into the blood, and then into the brain.

The well-known and most often used way of absorption of different medicines is through the mouth (orally). It is the simplest, but most psychoactive substances, because of their amino-nature, penetrate into the blood only when they get into the intestines, where there are basic reactions present in the milieu. This is the reason, for which by oral absorption, the effect comes relatively slowly; depending on how full the stomach is, this period of time can vary from 0,5 to 1,5 hours. The effect of the substances, which are being absorbed, while they are still in the stomach – alcohol, caffeine, barbiturates - comes considerably faster. The digestive system has also another end but the anal receiving is very rarely used (just imagine what would this look like if you were in a company), although in this way the substance immediately gets into a milieu with proper acidity and its absorption is sped up.

The classical notion of a drug-addict is connected with the venous injection. When this method is conducted, literally, after several heartbeats the substance is distributed evenly into the body and the quickness of the effect depends only on the speed, with which it penetrates into the brain. This is indisputably the most direct and effective way of creating a high concentration of a substance into the blood, but it is too risky.

The muscular or subcutaneous injection is also often used, but in this way the effects come considerably more slowly and they are also weaker.

Another well-known way of absorption is through the respiratory system. It creates the normal gas exchange and through it every volatile enough substance can get into the organism. The penetration of a substance through the alveoli of the lungs is very fast and almost so effective as the venous injection. The vapors of the very volatile substances can be simply inhaled, while the less volatile ones should evaporate. This usually comes about when they are smoked; by this way of absorption the vapors condense in the guise of aerosol, which fragments are as big as about 1 micron each – in other words this is a smoke, which is inhaled. The effectiveness of smoking depends strongly on the way of smoking, as the fume-fragments should have time to stick to the alveoli’s surface, from where the active substance diffuses into the blood. Smoking is the "dirtiest way" of absorption, a considerable part of the active substance burns, except it, together with it, also many other unnecessary and harmful substances are inhaled – tar, carbon oxide and even hydrocyanogen. Smoking, using narghile (water-pipe), urges to a certain extent the fume; in this way tobacco and hashish are smoked. For the inhalation of fumes, devices are created with external combustion, with which the substance is heated up, without burning away; an example for such a device is the pipe designed for smoking of opium. Lately, quite a simple method is being used, with which the substance is put on a tinfoil, which is heated up and then the fumes are inhaled through a narrow tube. These methods are a bit "cleaner" than smoking.

Chewing and sucking are much more effective ways of absorption than swallowing, especially for substances like cocaine and nicotine, which degrade quickly in the stomach and in the liver. The powder-like substances with size of the fragments of about 10 microns are sniffed. They do no reach the lungs and stick to the nose’s mucous membrane. Smearing the most tender places of the skin with special ointments was once practiced only by witches and mages.


"Drugs- One-way Ticket to Paradise". Created by team ID: C0115926 participating inThinkquest Internet Challenge 2001. All rights reserved.