Quitting smoking is not easy, as anyone who has tried to do it knows. The average smoker often makes several attempts to quit before giving up cigarettes for good.

It's a classic case of, “If at first you don't succeed, try, try again.” Smokers struggling to quit are more likely to be successful if their treatment regimen is changed or the dose of the drug varenicline was increased, researchers at MD Anderson Cancer Center at the University of Texas in Houston found.

The team also reported that varenicline, a medication to help smokers quit that is marketed under the brand name Chantix, was more effective than combined nicotine replacement therapy (CNRT) with a nicotine replacement patch and lozenges.

Those who manage to quit smoking within a few weeks of starting treatment have a good chance of remaining smoke-free over the long term, but they should continue taking their medication for at least 12 weeks, if not 24 weeks.

Healthcare providers who treat people for smoking cessation usually urge patients to stay on the same medication and return in six weeks. The problem is that most people who try to quit smoking will have relapsed by then, Paul Cinciripini, lead author on the study, told TheDoctor. That's why providers should be following patients closely, and not wait until the end of a 12-week treatment period to measure the response. “If treatment is not working early, do something different.”

If you manage to quit smoking within a few weeks of starting treatment, you have a good chance of remaining smoke-free over the long term, but you should continue taking the medication for at least 12 weeks, if not 24 weeks. “There is no reason to put yourself at risk [for starting smoking again] any sooner than you should,” Cinciripini said. Smokers trying to quit should talk to their providers about other treatments or increasing the dose of their current medication.

To compare the effectiveness of different treatment regimens at different doses, the study recruited 490 people who smoked on average 20 cigarettes per day. It used a sequential multiple assignment randomized trial (SMART) study design.

Participants were randomly selected to receive either six weeks of 2 mg of varenicline or combined nicotine replacement therapy in the form of a 21 mg patch and a 2 mg lozenge.

After six weeks, those who did not quit smoking either continued to receive the same regimen, switched to the other regimen or were given 3 mg of varenicline or a 42 mg patch and a 2 mg lozenge for another six weeks.

Smokers taking varenicline who did not quit at the end of the first phase were seven times more likely to quit if their dose of the drug was increased in phase 2, compared to those who stayed on the same dose or switched to CNRT. Those who switched from CNRT to varenicline in phase 2 were twice as likely to quit than those who continued on the same dose of CNRT.

Twenty percent of the participants who had their varenicline dose increased in phase 2 were still smoke-free six weeks later. Those who switched from CNRT to varenicline or who had their CNRT dose increased had a 14 percent quit rate.

None of the participants who took varenicline and then switched to CNRT in phase 2 stayed smoke-free for six weeks. After six months, only those who had initially failed to quit and who had their varenicline or CNRT dose increased were still smoke-free.

“The whole purpose of this line of research is to give providers and smokers more treatment options at a time when nicotine addiction has fewer options that any other chronic disease,” Cinciripini, head of the tobacco research and treatment program at MD Anderson, said. To expand patients' options, he and his team are currently running a new study that offers four more treatment options to help smokers quit with the same SMART design.

The study is published in JAMA: Journal of the American Medical Association.