The use of smoking cessation treatments improved smokers' chances of quitting, a systematic review and meta-analysis showed.
Both nicotine replacement therapy (NRT) and bupropion were superior to placebo in helping patients quit (odds ratio [OR] for NRT 1.84, 95% CI 1.71-1.99; OR for bupropion 1.82, 95% CI 1.60-2.06), wrote Kate Cahill of the University of Oxford in England, and colleagues.
When compared against one another, NRT and bupropion showed equal efficacy (OR 0.99, 95% CI 0.86-1.13), they wrote online in the Cochrane Database of Systematic Reviews
.
Use of varenicline, cytisine and nortriptyline also improved the chances of quitting, they noted.
The reviews were conducted between 2008 and 2012, analyzing 267 trials covering 101,804 smokers. Treatments studied included NRT, antidepressants (bupropion and nortriptyline), nicotine receptor partial agonists (varenicline and cytisine), anxiolytics, selective type 1 cannabinoid, receptor antagonists (rimonabant), clonidine, lobeline, dianicline, mecamylamine, Nicobrevin, opioid antagonists, nicotine vaccines, and silver acetate.
All the reviews used randomized controlled trials, and compared treatment with placebo and sometimes with other treatments, the authors wrote. A successful outcome was defined as 6 months' smoking cessation from the end of treatment.
Varenicline increased the odds of quitting compared with placebo (OR 2.88, 95% CI 2.40-3.47). It also showed superiority to single forms of NRT and to bupropion, they stated.
Varenicline also emerged as more effective than the nicotine patch, nicotine gum, and NRT inhaler, spray, tablets, and lozenges, the review stated. However, it was not more effective than combinations of NRT.
Combination NRT also outperformed single formulations. NRT inhaler, spray, tablets, and lozenges performed similarly against each other; all were marginally more effective than NRT gum (OR 1.21, 95% CI 1.01-1.46), the review found.
The nicotine receptor partial agonist cytisine -- available only in Russia and Eastern Europe -- returned positive findings (RR 3.98, 95% CI 2.01-7.87) without significant or serious adverse events, the authors reported.
The antidepressant nortriptyline also increased the chances of quitting (RR 2.03, 95% CI 1.48-2.78). Neither nortriptyline nor bupropion were shown to enhance the effect of NRT compared with NRT alone, they wrote.
Although most treatments did not appear to have adverse events that would mitigate their use, that was not the case with clonidine, the authors wrote. Clonidine increased the chances of quitting (RR 1.63, 95% CI 1.22-2.18), but was negated by a dose-dependent rise in adverse events.
They also found that mecamylamine combined with NRT may increase the chances of quitting, but the evidence remained inconclusive. Other treatments failed to demonstrate a benefit compared with placebo.
Nicotine vaccines are not yet licensed in the U.S. for smoking cessation. Nicobrevin's UK license has been revoked, and the manufacturers of rimonabant, taranabant and dianicline are no longer developing or testing those treatments, the authors noted.
The authors said their meta-analysis was limited by how recent the source reviews were. They also noted that "We have not included NRT in our meta-analyses of [serious adverse events], since coverage of this information was patchy or absent from many trial reports."
Funding was provided by the Department of Primary Care Health Sciences at the University of Oxford, the National School for Health Research School for Primary Care Research, and the National Institute for Health Research.
