Drug effective in smoking cessation studies
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An experimental smoking cessation drug by Pfizer Inc. was more effective than GlaxoSmithKline Plc’s rival medication in important late-stage studies, although the contrast was far less pronounced in the follow-up period, researchers said on Tuesday.
The 12-week studies, which Pfizer is expected to use to seek approval of the drug, showed 44 percent of smokers using Pfizer’s varenicline were able to quit. That compared with 30 percent among those using Glaxo’s Zyban, also known by the chemical name bupropion, and just 17.7 percent in the placebo group, according to data presented at the American Heart Association annual scientific sessions.
But the effect of the Pfizer drug was far less pronounced during a 40-week observation period following the studies of about 2,000 smokers.
During the ninth through 52nd week, researchers measuring continuous abstinence found a 22.1 percent rate for varenicline, compared with 16.4 percent for Zyban, a difference not considered statistically significant.
In a second study, varenicline did only slightly better, 23 percent to 15 percent for Zyban. Both drugs were much better than placebo in both studies.
A single puff of a cigarette counted as a return to smoking in the studies.
“Varenicline is a leap forward for smokers and if it is approved it will be part of my doctor’s bag,” said Dr. Serena Tonstad, a professor of nutrition at the University of Oslo who led the Pfizer-sponsored trial.
She said the drug is an attractive alternative to Zyban, which some patients cannot take because of allergic reactions and rare seizures linked to it.
Tonstad said people who successfully stayed off cigarettes well after the Pfizer treatment ended were able to do so largely with support from clinicians.
Varenicline works by partially stimulating and binding to the receptors in the brain that channel the rewarding, habit-forming properties of nicotine, researchers said.
Tonstad said there was no sign that the drug continues to exert a chemical effect on the brain very long after the patient stops taking it.
Pfizer shares were down 29 cents, or 1.3 percent, at $21.96 in morning New York Stock Exchange trade, where Glaxo fell less than 1 percent to $52.66.
On average, men who smoke die 13.2 years younger than nonsmokers, according to a 2004 report by the U.S. Surgeon General, while female smokers die 14.5 years younger than nonsmokers.
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