Alcohol comes in many forms, from beer and wine to spirits. It is a controlled but legalised drug in the sense that it is available only through certain licensed outlets and to persons over 18 years of age. Alcohol is a major contributor towards ill-health and disease in the UK, and leads to greater loss of life than any of the other drugs discussed in this section. Alcoholism is a widespread problem in the UK

Alcohol has a depressant effect; it relaxes the central nervous system and leads to a pleasant and uninhibited feeling. Most people feel merry and relaxed after a couple of drinks, but greater alcohol use can lead to poor co-ordination, exaggerated emotional reactions and eventually unconsciousness. Large amounts of alcohol may lead to coma and death.

Long-term consumption of large quantities of alcohol can lead to liver damage, heart disease and brain damage. Alcoholics frequently have poor nutrition and consequent poor health.

There is no evidence that moderate drinking is harmful, and many people find that a few drinks help to relieve feelings of stress or anxiety. Moderate drinking is also linked to a reduced risk of heart disease, although it is unclear why.

Small amounts of alcohol, especially before a meal, can help to increase appetite which can be valuable when someone is at risk of weight loss.

The government recently changed their advice on safer drinking. The recommended consumption has increased from 14 to 21 units per week for women and from 21 -28 units for men. However, the advice is that women should only drink 2-3 units per day and men 3-4 units per day. This advice comes about to address the issue of binge drinking which recognises that drinking all units in 1 or 2 sessions per week can be more detrimental to health than drinking a small amount every day. (http://www.alcoholconcern.org.uk/). However, heavy drinking can affect your immune system and may slow down recovery from infections. People who drink heavily often tend to neglect their diets.

Alcohol can react badly with some medicines, so it is best to check with the pharmacist or doctor when prescribed new medications to find out whether it is safe to drink alcohol with them. There is a particular problem with some treatments for tuberculosis (rifampicin and rifabutin) and the antibiotic metronidazole and related drugs. However, there is no direct incompatibility between alcohol and any of the current antiretrovirals (see section later on drug interactions).

Until this year there was little evidence that alcohol had any effect on HIV. However a 2005 study of monkeys given large doses of alcohol – the equivalent of four pints of beer a day over a seven-week period - found that rates of viral replication and viral load increased by 1.9 logs (nearly 89-fold). However although CD4 counts initially declined faster in monkeys given alcohol than the control animals, the difference in CD4 cells was not significant by the end of the study.

Cohort studies in humans have failed to find any association between alcohol use and progression to AIDS or infectiousness.