Smokers who try to quit using the drugs varenicline (Chantix) and bupropion (Wellbutrin) together are more successful in the short term than those who use Chantix alone, a new study finds.

The study of 315 smokers looked at quitting rates over 12 weeks in patients who used both drugs, compared with those who used only Chantix. At the end of 12 weeks, 53 percent of those taking both drugs had quit smoking, compared with 43 percent of those taking Chantix alone. After one year, 31 percent who took both drugs were still smoke free, compared with 25 percent who had used only Chantix, according to HealthDay.

“We believe this evidence strongly supports the idea that varenicline helps everybody quit,” said lead researcher Dr. Jon Ebbert of the Mayo Clinic. “But for heavier smokers and more dependent smokers, combination therapy with varenicline plus bupropion will increase quit rates more than varenicline alone.” He explained the two drugs work in different ways to help smokers battle their addiction.

Heavier smokers benefitted more from combination therapy than lighter smokers, the study found. “For lighter smokers, using varenicline alone is just as effective as using both medications together,” Dr. Ebbert said in a news release. “But, if you’re a heavy smoker, you really should consider using combination therapy to increase your success of quitting.”

The study appears in the Journal of the American Medical Association.