In all patients, the most common adverse effect from varenicline was nausea, which overall affected about 30% of those taking the drug. In about two-thirds of people who had nausea, the effect was mild. Other reported adverse effects were headache and vivid dreams. In general, varenicline appeared safe and was well tolerated, said Dr. Tonstad, but she did not report any data on hepatic and renal function in patients taking the drug. Weight gain was similar in the varenicline and placebo groups.
Varenicline prevents nicotine from binding to its receptor and helps break addiction, said Dr. Serena Tonstad. Catherine Hackett