Alcohol Consumption - Toxicology

Toxicology

Ethanol is metabolized into energy in the liver. In the liver, the enzyme alcohol dehydrogenase oxidizes ethanol into acetaldehyde, which is then further oxidized into harmless acetic acid by acetaldehyde dehydrogenase. Acetic acid is esterified with coenzyme A to produce acetyl CoA. Acetyl CoA carries the acetyl moiety into the citric acid cycle, which produces energy by oxidizing the acetyl moiety into carbon dioxide. Acetyl CoA can also be used for biosynthesis. Acetyl CoA is the energy-carrying intermediate common to the metabolism of sugars and fats; it is the product of glycolysis, the breakdown of glucose.

When compared to other alcohols, ethanol is only slightly toxic, with a lowest known lethal dose in humans of 1400 mg/kg (about 20 shots for a 100 kg person), and an LD₅₀ of 9000 mg/kg (oral, rat). Nevertheless, accidental overdosing of alcoholic drinks, especially those containing a high percentage of alcohol, is risky, especially for women, lightweight persons, and children. These people have a smaller quantity of water in their bodies, so that the alcohol is less diluted. A blood alcohol concentration of 50 to 100 mg/dL may be considered legal drunkenness (laws vary by jurisdiction). The threshold of effects is at 22 mg/dL.

In the human body, ethanol affects the gamma-aminobutyric acid (GABA) receptors and produces a depressant (neurochemical inhibitory) effect. Ethanol is similar to other sedative-hypnotics such as barbiturates and benzodiazepines both in its effect on the GABA_A receptor, although its pharmacological profile is not identical. It has anxiolytic, anticonvulsant, hypnotic, and sedative actions similar to many other sedative-hypnotic drugs. Ethanol is also cross-tolerant with benzodiazepines and barbiturates.

Alcohols are toxicated into the corresponding aldehydes and then into the corresponding carboxylic acids. These metabolic products cause a poisoning and acidosis. In the case of alcohols other than ethanol, the aldehydes and carboxylic acids are poisonous, and the acidosis can be lethal. In contrast, fatalities from ethanol are mainly found in extreme doses associated with the induction of unconsciousness or chronic addiction (alcoholism).