A new study has found that it’s the pace of nicotine metabolism in a smokers’ body that determines how quickly they will quit the smoking habit and what’s the most effective way to do so.

The findings were concluded in a first-of-its-kind largest randomised clinical study of tobacco dependence treatment.

The researchers found that the normal metabolisers of nicotine showed better quit rates due to the use of non-nicotine replacement therapy drug varenicline (also called Chantix or Champix) in comparison to the nicotine patch when the treatment ended as well as six months later. On the other hand, slow metabolizers were found yielding similar quitting success rate due to the use of nicotine patch, but without the side-effects reported with varenicline.

According to the researchers, Pfizer’s Varenicline was equally effective as a nicotine patch in helping the smokers kick their habit. However, Varenicline reported more overall side-effects among the smokers.

Detailing the study, lead author Caryn Lerman, said, “Matching a treatment choice based on the rate at which smokers metabolise nicotine could be a viable strategy to help guide choices for smokers and ultimately improve quit rates.”

Lerman is a Psychiatry professor and director of the Center for Interdisciplinary Research on Nicotine Addiction at Penn’s School of Medicine.

Nicotine metabolism and the slow and normal metabolisers illustrate how long nicotine consumed from cigarettes stays in the body after quitting the habit.

For the study, 1,246 treatment-seeking smokers were involved and then divided into two group- slow metabolisers (662) and normal metabolisers (584).

They were randomised to 11-weeks of either varenicline (plus placebo patch), the nicotine patch (plus a placebo pill) or a placebo pill and patch. All the participants also received behavioural counseling during the trial period.

Concluding the findings of the study, the researchers said that varenicline was more effective in helping smokers quitting their habit that the nicotine patch among normal metabolisers. On the other hand, the efficacy was equivalent for both varenicline and nicotine patch among slow metabolisers. But smokers with slow nicotine metabolism reported more overall side effects from the drug, suggesting use of the patch more beneficial for them.

The findings of the study were published online in the journal Lancet Respiratory Medicine.