Abstract

Insofar as smokers regulate body levels of nicotine, nicotine replacement is expected to suppress the desire to smoke a cigarette. Our study was designed to test the hypothesis that i.v. replacement of nicotine will suppress daily intake of nicotine from ad libitum cigarette smoking and to compare the physiological effects of prolonged exposure to nicotine infused i.v. to the effect of smoking cigarettes throughout the day. Eight subjects received a 14-hr infusion of deuterium-labeled nicotine dosed to achieve levels of nicotine similar to those while smoking cigarettes for each individual (average, 33.1 mg; range, 17.7-49.9 mg) or saline (placebo). Cigarette smoking was permitted as desired. Nicotine infusion did not significantly affect the number of cigarettes smoked or the amount of tobacco burned, but nicotine intake from cigarette smoking was suppressed in all but one subject by an average of 24.6% (range, 4.0-51.2%). Down-regulation of levels of nicotine while smoking in response to infusion of nicotine was imprecise, which may be a result of psychosocial factors influencing smoking behavior along with the development of tolerance to toxic effects of nicotine as a consequence of prolonged exposure to nicotine. Intravenous nicotine and cigarette smoking increased average heart rate and blood pressure throughout the day and 24-hr urinary epinephrine excretion to a similar extent. Despite higher levels of nicotine when subjects smoked during infusion of nicotine, there were no additional nicotine-related effects. No adverse effects were noted; most subjects could not distinguish nicotine from saline.(ABSTRACT TRUNCATED AT 250 WORDS)