Is the nicotine metabolite ratio a useful tool to improve the effectiveness, safety, and adherence to quitting smoking? Systematic review of the literature and meta-analysis.

Introduction: We have carried out a systematic review of the literature (SRL) and a meta-analysis (MA) to answer: 1. Validity of the nicotine metabolite ratio (NMR) in improving the effectiveness of pharmacological treatments (PT) for smoking cessation (SC). 2.