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FARMINGTON, Conn., Aug. 15 -- Many patients taking Chantix (varenicline tartrate) to help kick the smoking habit could be spared the side effect of nausea if introduced to the drug gradually, according to researchers here.

Titrating the dose of Chantix during the first week of treatment led to a drop of six to seven percentage points in the proportion of patients who became nauseated, said Cheryl Oncken, M.D., of the University of Connecticut Health Center here.

Nausea is a common side effect that sometimes causes patients to discontinue treatment, Dr. Oncken and colleagues reported in the Aug. 14-28 issue of the Archives of Internal Medicine. The study was supported by Pfizer, which makes Chantix. Pfizer was involved in all elements of this study, including, but not limited to, the study design and monitoring.

The study included nearly 650 patients who smoked an average of 21 cigarettes per day for an average of 25 years. Participants were randomized to a placebo group or one of four treatment groups: 0.5 mg Chantix non-titrated, 0.5 mg Chantix titrated, 1.0 mg Chantix non-titrated, 1.0 mg Chantix titrated.

In both titrated groups, the dose started out at 0.5 mg once daily. Over the course of seven days, the dose was gradually escalated to the full target dose, given twice-daily. The study followed participants as they attempted to quit smoking for 12 weeks, which is the usual course of treatment with Chantix, and then for an additional 40 weeks for a total follow-up of one year.

During treatment, 42% of the non-titrated 1.0 mg group became nauseated, versus 34% of the 1.0 mg titrated group (P not given). About 15% of the placebo group had nausea (P<0.001 compared with both treatment groups).

In addition, 23% of the non-titrated 0.5 mg group experienced nausea versus 16% of the titrated 0.5 mg group (P not given). Neither of these nausea rates differed significantly from the placebo rate (P=0.12 for the non-titrated group; P=0.86 for the titrated group).

Although the researchers did not report P values for the different nausea rates in the titrated versus non-titrated dosage groups, they concluded that "titration during the first week of treatment appeared to reduce the incidence of nausea."

The smoking abstinence rate through week 52 of the study, confirmed by breath measurements of carbon monoxide, was 4% for the placebo group, 22% for all patients receiving 1.0 mg twice daily (P<0.001 versus placebo), and 18.5% for all those receiving 0.5 mg twice daily (P<0.001 compared with placebo), the study found. These results were in line with previously published data.

Chantix was approved by the FDA last May 11. The drug is thought to be an a4ß2 nicotine receptor antagonist, blocking the rewarding effects of nicotine. But the drug is also believed to be a partial agonist to this receptor, stimulating enough dopamine release to reduce nicotine withdrawal cravings.

In an accompanying editorial in the Archives, Bankole A. Johnson, D.Sc., M.D., Ph.D., of the University of Virginia called Chantix a welcome alternative to nicotine replacement therapy and Zyban (bupropion) for doctors trying to help patients quit smoking.

"Varenicline was well-tolerated and promises to be more effective in clinical practice than bupropion," Dr. Johnson said. "Now, a smoker who wants help to quit no longer has a legitimate excuse to delay seeking treatment."

Four of the authors reported a variety of financial relationships with Pfizer and an additional four authors are employees of Pfizer.

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