Limitations
This study has the following limitations: 1) Limited by the search language and authority, we only searched English literature, and may miss some studies that meet the inclusion criteria, which may lead to potential publication bias or language bias. 2) Limited by the search time, new trials may appear in the future, which may lead to changes in the current research results, and we will update it in two years. 3) Different clinical trial studies have different reports on the outcomes of quitting smoking. Some studies use cotinine-confirmed prolonged smoking abstinence, while others use the 7-day point prevalence abstinence. The differences in the reporting methods of quitting smoking outcomes may affect the summary results. Therefore, it is necessary to carefully evaluate the combined effect. 4) A further subgroup analysis was not conducted, we cannot clearly assess the impact of some variables on the current level of evidence. Due to the limited number of studies on specific drugs, we did not analyze the potential effects of age, smoking status, alcohol consumption, drug dosage, duration, etc. on the outcome of smoking cessation.