Ethyl alcohol is a typical drug possessing a general (nonselective) depressant effect on the CNS. Besides, it has a marked antiseptic action.
Ethyl alcohol is of limited interest for medical practice. It is mainly used as an antiseptic (see Chapter 26). It is much more interesting from a social point of view, since alcohol consumption is often associated with acute and chronic poisoning.
After oral intake ethyl alcohol is quickly absorbed mainly in the small intestine and also in the stomach (about 20%). The absorption rate significantly depends on the gastrointestinal tract contents and peristalsis intensity. The systemic action of ethyl alcohol starts especially quickly when it is taken on an empty stomach. Fats and carbohydrates delay its absorption substantially
In the body up to 90% of the introduced amount metabolizes to CO2 and water. Oxidation of ethyl alcohol occurs in the liver (with the approximate rate of 10 ml/h), which is associated with the release of a substantial amount of energy (7.1 kcal/g). Long-term use can lead to the induction of hepatic enzymes, which in turn increases the inactivation rate of ethyl alcohol.
Lungs, kidneys and sweat glands eliminate ethyl alcohol in an unchanged form.
The systemic action of ethyl alcohol is mainly directed at the CNS. It has inhibitory CNS action that is proportionate to the increase of ethyl alcohol concentration in the blood and in the brain. CNS inhibition has three main stages (Fig. 6.1): 1) excitatory stage; 2) anesthetic stage; 3) medullary depression stage.
The excitatory stage is the result of suppression of the inhibitory mechanisms in the brain. Usually it is prominent and prolonged. Euphoria occurs, mood is improved, and the individual becomes excessively communicative and talkative. At the same time psychomotor reactions, the individual's behavior, self-control, adequate evaluation of the surrounding situation and working capacity are impaired.