Symptoms of nicotine toxicity in subjects achieving high cotinine levels during nicotine replacement therapy

Introduction: Nicotine replacement therapy (NRT) aids smoking reduction and cessation. Although NRT is effective and safe, some smokers may achieve high nicotine levels. The purpose of this study was to determine the incidence and severity of nicotine-related adverse events in subjects with levels of cotinine, a metabolite of nicotine, that increased by >50%, compared with baseline smoking in controlled clinical trials of NRT. Methods: Data from participants in randomized, double-blind, controlled trials of various formulations of NRT (Nicorette®) including patch, gum, oral inhaler, sublingual tablet, nasal spray, mouth spray, and combinations were extracted from a clinical database. Eligible studies were performed between 1989 and 2010. In addition to baseline, at least one subsequent plasma or salivary cotinine concentration was measured, and adverse events were recorded simultaneously. Of 28 eligible studies, 24 were smoking cessation studies, and 4 were smoking reduction studies. Results: Cotinine levels that increased by >50% above baseline were recorded during treatment in 746 of 7,120 subjects (10.5%). Nausea was reported in 16 subjects (0.2% of the total, upper 99% confidence limit [CL] 0.4%), vomiting in 2 subjects (0.0%, upper 99% CL 0.1%), palpitations in 5 subjects (0.1%, upper 99% CL 0.2%), dizziness in 11 subjects (0.2%; upper 99% CL 0.3%), and headache in 35 subjects (0.5%, upper 99% CL 0.7%). Conclusion: Typical symptoms indicating nicotine overdose together with high cotinine levels were rare during treatment with NRT. These findings support the safety of NRT for smoking cessation or reduction. © The Author 2014. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved.