Ethanol
Ethyl alcohol( ethanol , C2H5OH) has a sedative-hypnotic effect. When ingested, ethanol, as well as methanol, ethylene glycol and other alcohols, is easily absorbed from the stomach( 20%) and the small intestine( 80%) due to its low molecular weight and lipid solubility. The rate of absorption depends on the concentration: for example, in the stomach it is maximal at a concentration of approximately 30%.Ethanol vapor can easily be absorbed into the lungs. After taking ethanol on an empty stomach, the maximum concentration in the blood is reached after 30 minutes. The presence of food in the intestine delays absorption. The distribution of ethanol in the body tissues occurs quickly and evenly. More than 90% of the ethanol supplied is oxidized in the liver, the remaining is released through the lungs and kidneys( within 7-12 hours).The amount of alcohol oxidized per unit time is approximately proportional to body weight or liver mass. An adult can metabolize 7-10 g( 0.15-0.22 mole) of ethanol per hour.
Ethanol metabolism is mainly carried out in the liver with the participation of two enzyme systems: alcohol dehydrogenase and microsomal ethanol oxidizing system( MEOS).
The main pathway of the metabolism of ethanol is associated with alcohol dehydrogenase - the Zn ^ -containing cytosolic enzyme that catalyzes the conversion of alcohol to acetaldehyde. This enzyme is found mainly in the liver, but is present in other organs( for example, in the brain and stomach).In men, a significant amount of ethanol is metabolized by alcohol gastric dehydrogenase. The MEOS includes oxidases with a mixed function. The intermediate product of ethanol metabolism with the participation of the MEOS is also acetaldehyde.
It is believed that when the alcohol concentration in the blood is below 100 mg%( 22 nmol / L), its oxidation is mainly carried out by alcohol dehydrogenase, whereas at higher concentrations, the MEOS begins to play a more significant role. At present, it has not been proven that with alcoholic alcohol consumption alcohol dehydrogenase activity increases, but it is reliably established that the activity of MEOS increases. More than 90% of acetaldehyde, formed from ethanol, is oxidized in the liver to acetate with the participation of mitochondrial aldehyde dehydrogenase. Both reactions of ethanol conversion are NAD-dependent. Deficiency of NAD as a result of its consumption during alcohol intoxication can block the aerobic metabolism and limit the conversion of the final product of the glycosylation of carbohydrates and amino acids - lactic acid. Lactate accumulates in the blood, causing metabolic acidosis.
The mechanism of action of alcohol on the CNS is unknown. At the same time, it has been established that non-physiological concentrations of ethanol inhibit ion pumps responsible for the generation of electrical nerve impulses. As a result, alcohol suppresses the functions of the central nervous system, like other anesthetics. Alcohol intoxication develops typical effects of a sedative-hypnotic overdose along with cardiovascular effects( vasodilation, tachycardia) and gastrointestinal irritation. The relationship between the concentration of ethanol in the blood and the clinical manifestations of intoxication is presented in the table. The lethal dose of
ethanol in a single dose is from 4 to 12 g per 1 kg of body weight( an average of 300 ml of 96% ethanol in the absence of tolerance to it).Alcoholic coma develops at a concentration of ethanol in the blood above 500 mg%, and death - above 2000 mg%.
Table Dependence between ethanol concentration in blood and urine, and clinical manifestations of intoxication
Table Dependence between ethanol concentration in blood and urine, and clinical manifestations of intoxication
Instability of gait, indistinct speech and difficulties in performing simple tasks become apparent with ethanol concentration in blood plasmaabout 80 mg%.In this regard, in a number of countries this value serves as a boundary for prohibiting the management of motor vehicles. The mastery of the driver is reduced, even at lower ethanol concentrations. In Fig.the relative probability of a road traffic accident is shown depending on the concentration of ethanol in the blood [Graham-Smith DG, Aronson JK, 2000].
When determining the concentration of ethanol in serum, it should be borne in mind that it is 10-35% higher than in blood. When using the method of determining ethanol with alcohol dehydrogenase, other alcohols( for example, isopropanol) can serve as substrates and cause interference, which leads to false positive results.
The degree of intoxication depends on three factors: the concentration of ethanol in the blood, the rate of rise in the level of alcohol and the time during which an increased level of ethanol in the blood is stored. The nature of consumption, the condition of the gastrointestinal mucosa and the presence of drugs in the body also affect the degree of intoxication.
To assess the level of ethanol in the blood, the following rules should be used.
?The peak concentration of alcohol in the blood is reached after 0.5-3 hours after taking the last dose.
?Every 30 grams of vodka, a glass of wine or 330 ml of beer increase the concentration of ethanol in the blood by 15-25 mg%.
Ethanol concentration, mg%
Fig. The relative probability of an accident in relation to the concentration of ethanol in the blood
Ethanol concentration, mg%
Fig. The relative probability of an accident in relation to the concentration of ethanol in the blood
?Women absorb alcohol faster than men, and its concentration in the blood is 35-45% higher;During the premenstrual period, the concentration of ethanol in the blood rises faster and to a greater extent.
?Taking oral contraceptives increases the concentration of ethanol in the blood and increases the duration of intoxication.
?The concentration of ethanol in urine is not very well correlated with its level in the blood, so it can not be used to assess the degree of intoxication.
?In older people, intoxication develops faster than in young people.
The respiratory tests currently used for determining alcohol have their own peculiarities and limitations. The concentration of ethanol in the exhaled air is approximately 0.05% of the blood concentration, i.e. 0.04 mg%( 0.04 mg / L) at a blood concentration of 80 mg%( 800 mg / l), which is sufficient to detect itrespiratory tests.
In Table.the estimated data on the time of detection of ethanol in the exhaled air, depending on the dose of alcohol taken.
Table Time of detection of ethanol by respiratory tests