Washington, April 7 : A new study in monkeys has suggested a novel strategy for treating cocaine addiction - a replacement drug that mimics the effects of cocaine but has less potential for abuse.
Researchers from Wake Forest University School of Medicine found that treating monkeys with amphetamine significantly reduced their self-administration of cocaine for up to a month.
"This suggests the possibility of developing an amphetamine-like drug for treating cocaine addiction. The research also demonstrates the usefulness for conducting studies in monkeys to test potential treatments," said Paul Czoty, Ph.D., lead author and assistant professor of physiology and pharmacology.
With both heroin and tobacco, there are treatments to replace the addictive drug with a drug that has similar effects on the body, but with less potential for abuse.
"With this strategy in mind, clinical researchers have turned to drugs currently available, including amphetamines. While it's unlikely that amphetamine itself will turn out to be the best treatment, these drugs allow us to prove the concept of using a replacement drug to combat cocaine addiction," Czoty said.
Czoty said that amphetamines have been used in clinical studies with some success.
His new research in monkeys helps identify the best dose and schedule for administering a replacement drug - as well as evaluate potential treatment candidates and estimate potential side effects.
For the study, researchers taught the monkeys to press levers multiple times to obtain food or a cocaine injection.
With each injection, the number of required lever presses increased so that the animal had to work harder for the cocaine.
"This procedure measures the strength of the reinforcing effects of drugs. Each injection requires more and more work and eventually it gets to the point where it's not worth it to the monkey because more than 1,000 presses are required," Czoty said.
Access to cocaine was then removed and the monkey was treated intravenously with an amphetamine 24 hours per day.
When researchers re-exposed the monkeys to cocaine one week later, they observed a dramatic decrease in responding for cocaine.
They tested three different doses of amphetamine and found that a moderate dose was most effective.
Researchers also found that the treatment decreased lever-pressing for food, which could be predictive of side effects in humans, but this effect disappeared within one week while the effect on responding for cocaine injections persisted for up to one month.
"This was a very positive finding - exactly what we had hoped to see. Cocaine use was significantly reduced - by about 60 percent," Czoty said.
The findings were presented at an annual meeting of the American Society of Pharmacology and Experimental Therapeutics in San Diego, Calif.