Existing Drugs To Fight Addiction?

Can the antidepressant Prozac help you kick cocaine? Can Ritalin, which is meant for hyperactivity? How about a blood pressure pill or medicine for muscle spasms?

If you're an alcoholic, could you get help staying sober by taking an anti-nausea drug used by cancer patients?

Scientists are exploring those questions right now. In fact, in the field of addiction medicine, one of the hottest sources of new drugs is ... old drugs.

Despite years of research, there is no drug approved in the United States for treating cocaine dependence. To find such a treatment, the National Institute on Drug Abuse is sponsoring human studies of 21 medicines already on the market for something else. That's about two-thirds of all the potential cocaine drugs being tested in people, says Frank Vocci, director of NIDA's pharmacotherapy division.

Over at the National Institute on Alcohol Abuse and Alcoholism, nearly all the potential alcoholism drugs tested in people under institute sponsorship over the past 10 years were previously approved for some other use, says Raye Litten, co-leader of the institute's medications development team.

While the strategy is hardly new, "it's been going on maybe just a bit below the radar screen" for most of the public, Vocci said.

It can certainly work. In 1997, for example, the government approved a stop-smoking pill called Zyban, which was in fact the older antidepressant Wellbutrin.

To be sure, experts haven't given up on developing new drugs. Most NIAAA-funded drug studies for alcoholism that are in early stage testing — not yet tried on people — are brand-new drugs, Litten said.

But the notion of examining current drugs for addiction-breaking potential holds several advantages. It's a lot cheaper to get federal approval for a new use of an old drug than to bring a completely new medicine to market. And experience with an existing drug gives an idea of its safety and dose range for possible anti-addiction effects, Vocci said.

He and others caution that people who happen to have medications on hand that show promise in such studies shouldn't give them to friends and family with addiction problems. That must be left to professionals. Experts also say that even effective anti-addiction medicines usually can't work by themselves, but must be used along with non-drug therapy.

The most straightforward approach to testing an existing drug is to follow its approved purpose, but in a different way. For example, some scientists are studying how to prolong the effects of naltrexone, now usually given as a daily pill for treating dependence on alcohol or opiates like heroin and morphine.

Dr. David Gastfriend of Massachusetts General Hospital and Harvard Medical School and other researchers recently reported that specially formulated naltrexone helped alcoholic men cut down on their drinking for a month when they received the drug as a shot in the buttocks.

Why is a monthly visit to a doctor better than just taking a pill every day?

"The pill requires a daily awareness that this is a dangerous disease and a rational decision to take the pill," Gastfriend said. "The problem with this illness is that on any given day, a person can feel, `No, it would be better if I could drink.' So you take the pill the first day and you have to make 29 more decisions" the rest of the month.

"But if you received an injection the first day, those 29 decisions have already been made," said Gastfriend, a paid consultant to Alkermes Inc., which is developing the formulation he studied, called Vivitrex.

More striking than just reformulating a drug is finding a new and apparently unrelated use for it. Here, scientists are guided by emerging knowledge about how addiction hijacks the brain.

Addicts apparently suffer from a combination of unusually strong desire for a drug and a weak inhibition against using it, Vocci said.

"These people essentially have a revved-up engine and thin brake pads," he said.

In the brain, scientists have found that cocaine produces euphoria by stimulating nerve circuits that communicate with a substance called dopamine. So they've looked for medications that can affect the activity of this dopamine system.

One is a decades-old old drug called baclofen (pronounced BAK-loe-fen), used to treat spasms, cramps and muscle tightness in people with multiple sclerosis or spinal problems. Steven Shoptaw, a researcher at the University of California, Los Angeles, recently published a preliminary, federally funded study that suggested it can cut cocaine use in addicts. A much larger study is now under way to confirm that, but for now the drug looks promising, Shoptaw said.

Other drugs that work in a similar way and that are being tested in cocaine addicts include the anti-seizure medications tiagabine, topiramate and a drug sold overseas as Vigabatrin.

Cocaine withdrawal symptoms might be eased by boosting the brain's depleted dopamine levels. So scientists are studying dopamine-boosting drugs like Ritalin, used for attention deficit hyperactivity disorder, and amantadine, used for flu and Parkinson's disease.

But addiction is complicated enough to involve many brain circuits, which in turn provide many targets for anti-addiction drugs. Inderal, a blood-pressure medicine, may reduce cocaine craving during early abstinence by interfering with the actions of another brain substance, norepinephrine. The antidepressants Prozac and Effexor, which boost levels of yet another brain chemical called serotonin, are also under study in cocaine dependence.

Then there's ondansetron (pronounced on-DAN-se-tron), which is normally used to prevent nausea and vomiting after cancer chemotherapy or surgery. Scientists are studying it for both cocaine and alcohol abuse, again for its action in the serotonin circuitry.

By Malcolm Ritter