title: Effects of cigarette smoking and carbon monoxide on nicotine and cotinine metabolism.
abstract: OBJECTIVE
  To examine the effects of cigarette smoking on the disposition kinetics of nicotine and cotinine, to determine the effects of cigarette smoking on pathways of nicotine and cotinine metabolism, and to test the hypothesis that carbon monoxide inhibits the metabolism of nicotine.
  
  
  METHODS
  Twelve cigarette smokers were studied in three treatment conditions, each lasting 7 days, during which they smoked cigarettes, breathed carbon monoxide to achieve carboxyhemoglobin levels similar to cigarette smoking, or breathed air. In each treatment condition, subjects received a combined infusion of deuterium-labeled nicotine (d2) and cotinine (d4), with measurement of disposition kinetics and urine metabolite profile.
  
  
  RESULTS
  Cigarette smoking significantly inhibited the metabolism of nicotine but had no effect on cotinine metabolism. Cigarette smoking markedly induced the O-glucuronidation of trans-3'-hydroxycotinine but had no effect on the N-glucuronidation of nicotine or cotinine. Carbon monoxide had no effect on nicotine or cotinine kinetics or metabolic profile.
  
  
  CONCLUSIONS
  This study confirms previous observations that cigarette smoking inhibits nicotine metabolism but disproves the hypothesis that this effect is due to carbon monoxide. Induction of glucuronidation must be considered in understanding the effects of cigarette smoking on drug metabolism.
authors.affiliation: Division of Clinical Pharmacology and Experimental Therapeutics, San Francisco General Hospital Medical Center, University of California, 94143-1220, USA. nbeno@itsa.ucsf.edu
authors.forename: N L
authors.initials: NL
authors.lastname: Benowitz
authors.forename: P
authors.initials: P
authors.lastname: Jacob
mesh_terms: D000328:Adult; D002248:Carbon Monoxide / Q000009:adverse effects* / Q000378:metabolism; D003367:Cotinine / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D020719:Glucuronides / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009538:Nicotine / Q000378:metabolism* / Q000493:pharmacokinetics; D012907:Smoking / Q000009:adverse effects* / Q000378:metabolism
chemical_list: D020719:Glucuronides; D009538:Nicotine; D002248:Carbon Monoxide; D003367:Cotinine