Israeli Study Finds: Smoking Cessation Drugs have Low Long-Term Efficacy

Smoking cessation drugs were shown to be effective in raising smoking avoidance rates in controlled randomized trials, but it is unclear how long their benefit lasts. A meta-analysis integrating the findings of 61 previous studies performed at Tel-Aviv University led to the conclusion that the percentage of smokers benefitting from the drugs declines during the first year of use. Nevertheless, 12 months from the beginning of the treatment, its benefit is still evident.

“Smoking cigarettes is the most common preventable cause of death in the world,” says Dr. Leah Rosen, head of the research team from the Department of Health Promotion at the School of Public Health of Tel Aviv University. “A variety of smoking cessation drugs were approved by the FDA and their efficacy was proven in controlled clinical trials, which were performed over a limited duration; their long-term efficacy remained an open question. We sought to examine this issue, focusing on the question whether the efficacy of these drugs declines over time.”

Rapid decline

In the study, which was published in the journal Addiction, researchers performed a meta-analysis – a statistical analysis of the results of numerous studies – and summarized the findings of 61 controlled trials from the international scientific literature. The studies included nearly 28 thousand smokers seeking to quit, and examined the efficacy of three common first-line FDA-approved drugs over time (3, 6 and 12 months from the beginning of treatment): Bupropion (marketed as Zyban), Varenicline (Champix) and nicotine replacement therapy (NRT).

Bupropion blocks the nicotine acetylcholine receptors, which are activated by the nicotine found in cigarettes. Blocking these receptors counters the effect of cigarette smoking on them, thus assisting smokers in quitting. Varenicline also affects these receptors, partially activating them. It leads to the decreased release of dopamine compared with that induced by nicotine from cigarettes, reducing the addictive effect of smoking. NRT is a group of non-smoking nicotine consumption methods (e.g., nicotine skin patches and chewing gums). Using them, smokers still consume nicotine, but avoid the act of smoking. This reduces the risk of lung cancer, which is a substantial cause of death in smokers.

In all studies, participants were randomly divided into groups: some received the drug and others, in the control group, received a placebo. During most trials, all participants – both in the treatment and control groups – were also offered personal counseling and professional psychological support throughout the withdrawal process.

The researchers found that about 40% of the treated participants did not return to smoking three months after the treatment. However, after six months, this rate dropped to approximately 25%.

A year after the beginning of the treatment, about 20% of those who received treatment managed to refrain from smoking, compared to only about 12% in the control group. By calculating the difference between the two groups, it appears that one year from the beginning of the treatment, smoking cessation drugs assisted only eight percent of the smokers who received them.

Limited time

The Tel-Aviv University study did not analyze trials examining smoking cessation for a period longer than one year from the beginning of the treatment. Most prospective studies on smoking cessation did not follow the participants for more than one year, and whether these treatments offer long-term aid remains an important question to be answered.

“According to our findings, eight of every 100 smokers did, in fact, benefit from the smoking cessation drugs, which, in itself, justifies the continued effort to use such medications,” concludes Rosen. “However, this is clearly not enough. We need to work harder to decrease smoking incidence in the population and reduce its damages. We believe it is imperative to find more effective methods to help smokers quit for good. Policymakers must use all possible means to prevent smoking initiation at a young age. Prevention of entry into the cycle of addiction is the best possible medicine.”

Translated by Elee Shimshoni