Recycled for rehab
Medications designed for one purpose often end up as treatments for other conditions. That’s not unusual. What is surprising is the number of older drugs that have suddenly become good candidates for treating cocaine addiction.
Researchers at the National Institute on Drug Abuse are studying whether half a dozen medications used for such conditions as narcolepsy and influenza can help people trying to abstain from cocaine and other addictive drugs.
Traditional therapy for cocaine addiction, which affects an estimated 1.5 million Americans, has centered on psychological counseling and behavioral therapy.
But scientists are increasingly using drugs to treat drug dependence, an effort stemming from an increased understanding of the brain’s own natural chemicals and how foreign substances affect the brain.
The first of these studies is on selegiline, an old antidepressant that is also used to help reduce the symptoms of Parkinson’s disease. NIDA researchers are expected to soon announce the results of a study in which 300 cocaine users were treated with either a selegiline skin patch or a placebo.
“Selegiline is what I call a first-generation drug for cocaine dependence. The majority of these will be drugs that are already marketed,” says Dr. Frank Vocci, director of medications development at the National Institute on Drug Abuse.
Because such drugs are already widely available, doctors have an idea of how they work in the body and how they might help treat drug dependence.
Selegiline is a monoamine oxidase inhibitor, meaning that it inactivates an enzyme that breaks down brain chemicals important to mood and well-being. MAO inhibitors fell out of favor years ago, however, because patients taking them can have severe toxic reactions, even death, if they consume foods containing tyramine, an amino acid found in cheese, sausage, soy sauce, beer and many other foods.
The cocaine dependence study is using a new formulation of selegiline: a skin patch that appears to avoid interactions with tyramine. The patch is being developed by Somerset Pharmaceuticals in Tampa, Fla.
“With the patch, there are no dietary restrictions,” Vocci says.
An earlier study in which cocaine users were given small doses of oral selegiline indicated that it can help blunt the high that users feel, thus curbing the desire to use again.
The drug elevates levels of a brain chemical called dopamine that appear to be eroded by the use of cocaine and nicotine (selegiline is also being tested for nicotine dependence).
But selegiline also appears to prompt the release of a chemical called phenyl ethylamine. This substance is often called the “love chemical,” Vocci says, because it’s found in chocolate and has been linked to feelings of love. The “love chemical” reputation is “urban science legend,” Vocci says. “It’s still an interesting compound.”
The institute has also launched a study on the effects of selegiline on methamphetamine dependence because methamphetamines also affect dopamine levels in the brain.
While selegiline is one of NIDA’s first attempts at testing medications for substance abuse, many other projects are underway. All of the studies, Vocci notes, will be using the medications along with behavioral therapies. Research has shown that such an approach is more effective than drug therapies alone, he says.
And, later this year, NIDA will launch a study on a cocaine vaccine. The goal is to prime the body to recognize cocaine as a foreign invader and generate antibodies. Study volunteers will receive injections of the vaccine and then will be followed for several months to gauge their cocaine use.
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Some pharmaceuticals could blunt addictions
Medications being tested for their ability to treat cocaine dependency and other substance abuse disorders:
* Disulfiram. Commonly known as Antabuse, disulfiram has emerged as one of the most promising among the older drugs that are now being tested as substance abuse medications, Dr. Frank Vocci says. The National Institute on Drug Abuse will soon start a large clinical trial to evaluate its effectiveness in blunting the pleasurable effects of cocaine.
* Amantidine. This flu remedy is also used for Parkinson’s disease. A previous study showed that amantadine and a beta blocker, propranolol, helped heavy cocaine users abstain from the drug. The drugs are now being studied separately and together.
* Baclofen. It’s used to relieve spasms and muscle cramps, usually in people with multiple sclerosis or spinal cord injuries. A recent study indicated it can reduce cocaine use.
* Naltrexone. Used to help prevent relapse in recovering alcoholics, naltrexone may also help prevent cocaine use.
* Modafinil. This medication, also known as Provigil, is used to treat narcolepsy. Very preliminary research suggests it could reduce the effects of cocaine and may act on a part of the brain involved in impulsive behavior.