Hangover is medically and biochemically very interesting condition, which is a direct consequence of intake of a larger amount of alcohol. The following description including the best treatment relies on biochemical and metabolic pathways leading to hangover symptoms.
Uncomfortable symptoms in hangover are caused by alcohol and by disruption of the internal environment of the organism. Alcohol (ethanol chemically) is in our body converted by an enzyme (alcohol dehydrogenase) to a substance called acetaldehyde. Acetaldehyde is further transformed by enzyme acetaldehyde dehydrogenase to acetate, which is an energy source. Alcohol and acetaldehyde have completely different effects on our body. Alcohol causes euphoria, loss of inhibitions and disturbance of consciousness. Acetaldehyde is a much more aggressive acidic substance that causes nausea, vomiting and headache, i.e. the classic symptoms of a hangover.
In addition, the alcohol affects our hormonal system. It blocks the action of antidiuretic hormone (ADH), which is produced in the brain. Antidiuretic hormone acts in kidney tissue and it prevents excessive loss of fluids. Disruption of the ADH effect causes dehydration. Have you ever wondered why there is such strong urge to pee after drinking few beers? This was the answer. The volume of ingested alcohol does not help and so even a person that drank 10 beers (few liters of fluid) will suffer from dehydration the morning after.
Dehydration leads to thickening of blood and the internal environment of the body. The concentration of most substances increases and technically this is called a hypertonic environment. However, the concentration of most important minerals (sodium, potassium, chloride) does not grow due to their losses by excessive urination.
Another aspect of a hangover is low blood sugar (hypoglycemia). The liver tissue is focused on eliminating the alcohol and does not have the capacity to release adequate amount of sugar to the blood.
The best prevention is, of course, responsible drinking of alcohol.
The treatment is rather symptomatic as the symptoms slowly withdraw. The affected person needs mostly rest and adequate intake of fluids (non-alcoholic of course). Some non-steroidal anti-inflammatory drugs may also have effect. Theoretically, the best therapy is intravenous hydration including administration of glucose and. Glucose infusion with added minerals (NaCl and KCl solutions) is effective against the hypoglycemia, brings missing fluid and minerals. Of course, this is just a theory as the hangover is not a condition that should be regularly treated by doctors.