Methadone can Treat, Reverse Cocaine Addiction, Prof Finds

November 27, 2008 - News Release

Methadone, typically used to treat heroin addiction, may also be effective in treating cocaine addiction, according to a new University of Guelph study.

Psychology professor Francesco Leri is the first to reveal that methadone can reverse key cocaine-induced neurobiological changes in the brain known to play a key role in addictive behaviours.

When rats were exposed to cocaine and then given methadone, they not only stopped exhibiting cocaine-seeking behaviour, but their brains also appeared to return to the way they were before taking the drug.

"This shows that methadone is capable of suppressing cocaine-seeking behaviour and cocaine-induced neural adaptation when administered after cocaine exposure."

The study, published in European Neuropsychopharmacology, first examined the impact methadone had on the behaviour of rats that were previously exposed to cocaine.

To measure the rats' cocaine-seeking behaviour, Leri trained the animals to associate a flashing light and the sound of a buzzer with an injection of cocaine. They were then placed in a chamber with a lever that, when pressed, reproduced the buzzer sound and flashing light.

Rats that weren’t given methadone before being placed in the chamber constantly pressed the lever, indicating cocaine-seeking behaviour, said Leri. Rats that received methadone showed no interest in the lever.

"This is important because the rats were exposed to the cocaine first and then given the methadone," he said. "This is a situation that has clinical relevance because it mimics what happens in humans. You first become an addict and then you get treatment."

Leri then studied the brains of the rats to see what impact the methadone had on the regions normally affected by cocaine.

"When someone is exposed to cocaine, the drug causes molecular changes in certain regions of the brain that are associated with drug-seeking behaviour and compulsive drug intake. What's interesting is that, among the rats given cocaine and then methadone, these regions of the brain looked similar to how they appeared in the rats that were never exposed to cocaine."

These findings support the use of methadone in treating cocaine addiction and confirm that this form of treatment is an "extremely useful pharmacological tool," he said.

"The next step is to look into medications that act like methadone but don't have the same side effects as potential treatments."

For media questions, contact Communications and Public Affairs: Lori Bona Hunt, 519-824-4120, Ext. 53338, or Deirdre Healey, 519-824-4120, Ext. 56982.

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