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A one-off dose of ketamine may help heavy drinkers cut back on alcohol, an experimental trial by University College London suggests.

When the sedative was used to disrupt people's memories of why they wanted to drink, they drank less and their urge to drink lowered over nine months.

The researchers say ketamine could be a helpful treatment for alcohol and other addictions.

Experts said the findings were worthy of further investigation.

What is ketamine?

Ketamine is widely used in the NHS as an anaesthetic, sedative and pain reliever.

It is also commonly used on animals.

Because of its hallucinogenic effects, it is also thought of as a "party drug".

But it can cause serious harm to the body, and be fatal, if used this way.

Ketamine is classed by the government as a Class-B drug, which means it is illegal to take, carry, make or sell.

Recreational use risks:

serious bladder problems

feelings of sickness

confusion

memory problems

paralysis of the muscles

hallucinations

depression

flashbacks

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What did the study find?

The study involved 55 men and 35 women who were drinking about 30 pints of beer a week - five times the recommended limit - but had not been diagnosed with alcohol addiction and were receiving no treatment.

First, they were shown pictures of beer and other drinks, asked to rate their urge to drink and the pleasure it would give them and then given a beer.

Next, they were split into three groups and:

the process was repeated but instead of a beer, they were given a small dose of ketamine via an intravenous drip

the process was repeated but instead of a beer, they were given a placebo (dummy drug) via an intravenous drip

the process was not repeated and they were given a small dose of ketamine via an intravenous drip

During the following nine months, all three groups managed to reduce their drinking.

But the first group had the greatest overall improvement:

cutting their alcohol intake by about half

drinking on fewer days

when given a small beer, having less urge to drink it and enjoying it less

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What do the experts say?

Lead study author Dr Ravi Das, a psychopharmacologist at University College London, said: "This is a first demonstration of a very sensible, accessible approach.

"We want to make treatment better for people with addictions, so we now need to replicate this in a full clinical trial."

Matt Field, a professor of psychology at the University of Sheffield, said the findings were "promising" and "worthy of further investigation".

But "further investigation with a larger sample size" was needed to support claims using ketamine to rewrite reward memories led to unprecedented long-lasting reductions in alcohol consumption.

Celia Morgan, a professor of psychopharmacology at the University of Exeter, said: "Ketamine is an addictive substance and associated with harms to bladder and a risk of accidents, so we have to be cautious when using it in groups who are prone to addictive behaviours.

"But this is important work trying to drive the science of ketamine and memory forwards."