Study selection and data extraction
Two reviewers independently conducted screening and data extraction, with any disagreements resolved by consultation with a third reviewer. After removing duplicate articles, two reviewers screened the titles and abstracts according to the inclusion criteria and then read the full-text articles to determine the final studies for inclusion.
A pre-set standardized form was used to extract the key information by two reviewers, independently. The data that were extracted from each publication included: (1) details of the study, such as the year of publication, study design, name of the first author, and country; (2) characteristics of the population, such as their age and cigarettes smoked per day; (3) details of the intervention, such as the drug name, dose, and duration of treatment; (4) treatment outcomes, including the number of people who successfully quit smoking and any adverse events.