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.