Trials showed that a combination of the drugs buprenorphine and naltrexone target two of the brain’s receptors identified in addiction to cocaine and opiates such as heroin.
The use of cocaine and heroin is a major public health issue, but despite this there is currently no effective relapse prevention treatment available. As many as 70 per cent of addicts relapse within the first year of treatment.
Recent reports suggest that illicit drug use in the UK alone cost in excess of £15 billion every year, and there are clear social and economic incentives to finding new ways to tackle drug dependency and addiction.
Most addicts use more than one substance and deaths from drug misuse more often involve a combination of drugs rather than a single compound. Frequently this combination includes opiates, cocaine and alcohol.
During trials, research funded by the Medical Research Council (MRC) provided the first evidence that such combinations could have a direct and beneficial effect in animal models of cocaine relapse. Trials also suggest the new combination treatment of buprenorphine and naltrexone could be effective at reducing alcohol intake in an addict population.
Report co-author Dr Chris Bailey from the Department of Pharmacy & Pharmacology, said: “Numerous neuronal systems are likely to be involved in drug addiction, so the approach we are taking is to target more than one of these at the same time. The benefit of a buprenorphine/naltrexone combination is that it targets both the mu-opioid and kappa-opioid systems at the same time, two receptor types previously identified as participating in drug addiction.
“This research is in its early stages, more pre-clinical work is needed but it’s encouraging to find a drug combination that appears to be effective against relapse to both cocaine and opiate drug-seeking behaviour.”
A significant challenge researchers are working to overcome is that buprenorphine and naltrexone currently need to be administered by different routes. An innovative solution currently investigated by the team would be to deliver both through the skin using iontophoresis – effectively an injection without the needle. The treatment would be implemented through a transdermal patch which uses a mild electric current to deliver the two compounds across the skin. Another approach being taken by researchers in the Department is to develop a single chemical entity that can replace the combination.
Professor Stephen Husbands, who is also part of the research team, added: “In work funded by the National Institute on Drug Abuse we have been successful in discovering compounds with the desired pharmacological profile, that also appear to share the relapse prevention activity of the combination. Being able to administer a single compound, rather than a combination of drugs, could have significant therapeutic benefit.”
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