A: Varenicline (Chantix) is a drug approved in 2006 by the FDA as an aid for cigarette smokers who want to quit.

Varenicline works two ways. It both imitates and blocks nicotine’s effect. When it works, it helps to cut down craving and withdrawal symptoms. It also gives a smoker less pleasure. In theory, this can reduce the discomfort of withdrawal. At the same time, it makes smoking less appealing.

In controlled studies, varenicline has been more effective than a placebo. It quadruples the chance of quitting in the short term. And it increases the likelihood of staying smoke free.The most common side effect is nausea, which usually is mild and improves over time. Other common side effects are headache, vomiting, gas, insomnia, abnormal dreams and changes in taste.

Experts disagree about varenicline and suicide risk. If there is an increased risk, that risk is quite small. In any case, immediately report any changes in mood or thinking to your doctor.

Varenicline is best taken with a full glass of water after a meal. The standard dose is 1 mg twice a day. Smokers usually start at a lower dose for the first week. It takes a little while for the right blood levels to be achieved. Therefore, wait a week or two before quitting cigarettes.

Varenicline compares well with other treatments. Like them, it works for only a minority of patients. So get psychological support. Psychotherapy or a support group can better your chances.

This drug is a valuable addition to the list of treatments for smoking cessation. The effects of smoking are devastating. Small gains in treatment can translate into millions of lives saved.