Phase of Addiction Has Big Impact on Effectiveness of Drug Treatment

By Victoria Kim 07/07/14

Study shows that certain drug treatments may be more effective in stopping drug seeking behavior in established addicts than in new addicts.

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The effectiveness of addiction treatment has a lot to do with the extent of an individual's addiction, a new study has found.

The University of Cambridge researchers conducted their experiment, which investigated pharmacotherapies for cocaine addiction, on 40 male rats to study how impulsivity and phase of addiction influence an individual’s response to drug treatment.

In order to measure impulsivity, the rats were trained to self-administer food pellets by pushing open a panel during certain periods. The rats were also trained to press a lever to self-administer cocaine dissolved in water. The researchers then monitored the extent to which the rats exhibited cocaine-seeking behavior, like pressing the lever even when cocaine is not delivered.

After administering a dopamine receptor-blocking drug called a-flupenthixol directly into the dorsolateral striatum (DLS) of the rats at various phases of addiction, most rats reduced their cocaine-seeking behavior. However, the extent of this behavior shift was also influenced by the inherent impulsivity of the rats. The more impulsive rats were not as affected by the drug as the rats who scored as being “low impulsive.”

More interestingly, rats in an early phase of addiction were not affected by the drug treatment. Rather, it was the rats that had a longer history of self-administering cocaine that exhibited the greatest change in behavior after receiving the drug. Therefore, it is suggested that an individual’s inherent lack of self-control has less to do with their vulnerability to addiction than their struggle to regain control over habits that have long been established in the brain.

“It is suggested that vulnerability to addiction conferred by impulsivity is less influenced by the propensity to develop drug-seeking habits and more by the inability of an individual to regain control over these habits that are rigidly and maladaptively established in the brain,” explained lead author Dr. Jennifer Murray.

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