Giving a shot of ketamine to heavy drinkers helped them feel the urge less to drink and a prolonged decrease in alcohol intake over nine months changed them altogether, according to an experimental study by the University of California team that was published in Nature Communications.
The researchers tried to upend the maladaptive reward memories that are central to drug and alcohol addiction in the brain. They experimented with 90 people who had harmful drinking behaviour, and they preferred beer. They were drinking 74 units of alcohol per week, equivalent to roughly 30 pints of beer - five times the recommended limit.
In the experiment, the participants were given a glass of beer but told they could drink it after finishing a task. On the first day, they were allowed to drink the beer after finishing the task but on the second day, the beer was unexpectedly taken away from them.
Reward system disrupted
Unexpectedly removing an anticipated reward is known to have a destabilising effect on retrieved reward memory. The brain then tried to undergo an active process to re-stabilise and store the memory. But ketamine prevents this memory re-storage process by blocking a receptor in the brain that is needed to restabilise memories.
On the key day, one third of the study participants were given an intravenous infusion of ketamine after the beer was taken away, while another group was given an infusion of a placebo. The other third were given ketamine, but without previously completing the drinking memory retrieval task.
Ketamine combined with memory retrieval
The method was successful, as over a 10-day period, the people who were given ketamine combined with memory retrieval showed "significant reductions in their urge to drink, compared to other study participants. They showed less urge to drink when given a small sample of beer and they enjoyed it less and had less desire to continue drinking than the other groups."
The effect was long lasting over a nine-month period. While all three groups decreased their drinking to some degree, those given the ketamine + memory retrieval had a much more a greater overall improvement -- they halved their average weekly alcohol consumption over the nine months.
The researchers conducted blood tests and found that the treatment was more effective in people where the ketamine was most readily available in their blood, suggesting that a higher dose may have led to greater improvement in some people.