A one-off infusion of the horse tranquiliser ketamine could help heavy drinkers reduce their alcohol intake, by switching off the feeling of reward, scientists have shown.

In an experiment involving 90 people who regularly consumed 30 pints of beer a week, scientists were able to retrain the brains of participants using the drug.

Participants on ketamine were told they were to receive a pint of beer, but scientists at University College London (UCL) then refused to hand over the alcohol.

Although that would have normally triggered a mental response of disappointment and loss, the drug prevented those memories from occurring, resetting their reward centres.

In the following 10 days, trial participants reported less urge to drink beer and in the following nine months their alcohol intake decreased considerably.

“We found that heavy drinkers experienced a long-term improvement after a very quick and simple experimental treatment,” said the study’s lead author, Dr Ravi Das of UCL Clinical Psychopharmacology Unit.

“Learning is at the heart of why people become addicted to drugs or alcohol. Essentially, the drug hijacks the brain’s in-built reward-learning system, so that you end up associating environmental ‘triggers’ with the drug. These produce an exaggerated desire to take the drug.