The Cochrane Library has published a review of the evidence supporting nicotine receptor partial agonists including varenicline.
The authors conclude that varenicline is three times more effective than placebo in achieving successful long-term smoking cessation and is more effective than bupropion based on the currently published trial data. They also highlight the need for comparative studies with nicotine replacement therapy and independent trials of varenicline versus placebo to confirm the findings of industry trial.
Finally, the authors state that the efficacy of varenicline as an aid to relapse prevention has not been clearly established.
Action: Nicotine replacement therapy remains the first line choice. Varenicline (and bupropion) are suitable alternatives where NRT treatment fails. Extended varenicline treatment to prevent relapse cannot be recommended until efficacy has been more clearly established.