Systematic review and meta-analysis investigating nicotine, cotinine and carbon monoxide exposures in people who both smoke and use nicotine replacement therapy.

People who smoke and also use nicotine replacement therapy report smoking less heavily than people who solely smoke. When nicotine replacement therapy is used in the lead-up to quitting (preloading), this reported smoking reduction has been biochemically confirmed. There is no evidence that concurrent smoking and nicotine replacement therapy use result in greater nicotine exposure than solely smoking.