Philadelphia ? Anthony Tarducci has tried to quit smoking many times over the last 25 years. He’s gone cold turkey, slapped on the patch, even taken antidepressants. Nothing worked.

On June 23 he tried again, this time with a powerful new aid: Chantix – the antismoking medicine that was approved for sale in the United States 18 months ago.

Today, the 45-year-old considers himself an ex-smoker, and he credits the drug with enabling him to kick his more-than-a-pack-a-day habit.

“What I found with everything else I tried was I still had that urge, I still had that craving,” says Tarducci. “When I was on Chantix I never had any of that. I just didn’t want to smoke anymore.”

And that, in a nutshell, is the difference between Chantix and other antismoking pharmaceuticals.

The others substitute a cigarette’s nicotine – the component that makes it physically addictive as well as pleasurable – with their own. Smokers can then quit the habit while getting their nicotine-induced pleasure elsewhere.

Chantix, on the other hand, was designed to give pleasure without nicotine.

The Pfizer drug, whose scientific name is varenicline, appears to work in two ways: It blocks nicotine from binding to receptors in the brain that trigger the release of dopamine, a chemical neurotransmitter that generates feelings of pleasure. At the same time, Chantix stimulates the brain to release some dopamine, which reduces symptoms of withdrawal.

Not a sure thing

But Chantix is still far from a sure thing. Less than half of smokers manage to stay off cigarettes during the typical 12-week prescription. Even fewer, just one in four, remain smoke-free after a year.

Robert Murray is one who didn’t make it.

At first he was able to cut four cigarettes a day from his pack-and-a-half habit. He soon found himself back where he started, and dropped the medication.

After two heart attacks, the 49-year-old is plenty motivated to quit. He knows his health problems are related to the 35-year habit, and he worries about not being around for his kids and grandkids.

So he’s planning to try again with a Chantix-boosted New Year’s resolution – after all, the drug worked better than anything else he’s tried.

Head-to-head comparisons have found it gets significantly better results than other anti-smoking aids. Researchers reported in the Journal of the American Medical Association last year that 23 percent of Chantix users still weren’t smoking 12 months later vs. 15 percent of those who relied on a commonly used antidepressant, burpropion, and fewer who quit cold turkey.

“Chantix is the most effective FDA-approved treatment for smoking,” says Freda Patterson, a project director at the University of Pennsylvania’s Transdisciplinary Tobacco Use Research Center. “Still, only a fraction of smokers looking to quit do so effectively.”

The reason, as she and other scientists have known for years, is that “smoking is a behavioral as well as a biological addiction.”

So while Chantix seems effective at blocking the biological impulse, many smokers still can’t break habits that they have integrated into their lives over decades – lighting up automatically after meals, for example, when stressed.

Kicking the habit

Changing her routine has been the challenge for Vienna Leoncavallo, who started smoking in her teens.

After using Chantix for six weeks so far, the 57-year-old says she no longer feels the need to smoke. Yet she’s still smoking.

“With me, it is totally the habit,” she says. “I just can’t get rid of those two little cigarettes with my morning coffee.”

Even so, Leoncavallo is pleased with the results of using Chantix, and doesn’t mind shelling out the $125 for a 30-day supply of shrink-wrapped tablets.

“They are not cheap,” she says, “but they are cheaper than cigarettes.”

The manufacturers’ instructions for Chantix suggest that patients not quit during the first week, while the dose is ramped up. After that they should try, and ideally stay off forever.

“You should take it for at least three months,” says Sandra Weibel, a pulmonary and critical-care doctor at Thomas Jefferson University Hospital. “In the studies they suggest that if you take it longer your chance of a relapse is less.”

Weibel says “the biggest hurdle with Chantix these days is that it is often not covered by insurance.”

Even without the boost of insurance coverage, sales of Chantix are brisk. More than six million prescriptions were filled during its first 13 months on the market, generating sales of $576 million, according to IMS Health, a healthcare information company in Plymouth Meeting, Pa.

This despite the drug’s common side effects: nausea, constipation, gas, vomiting, and, for some users, sleep disturbances that include strange or particularly vivid dreams.