title: Determinants of plasma concentrations of nicotine and cotinine during cigarette smoking and transdermal nicotine treatment.
abstract: OBJECTIVE
  Interindividual variability in plasma concentrations of nicotine and its proximate metabolite, cotinine, is considerable during smoking and transdermal nicotine treatment, even among individuals taking in nominally similar doses of nicotine. This report explores the determinants of this variability and the utility of baseline (smoking) plasma concentrations to predict concentrations during transdermal nicotine treatment.
  
  
  METHODS
  Data were analysed from a smoking cessation study (n = 466), and from a pharmacokinetic study (n = 12). Multiple regression models examined the relationships of plasma concentrations to individual characteristics such as smoking pattern, absorbed dose of nicotine, and pharmacokinetic parameters.
  
  
  RESULTS
  Plasma concentrations of nicotine and cotinine were highly variable in both studies. Indirect estimates of plasma clearance (baseline plasma concentration divided by cigarettes per day) together with other factors could account for 18 to 33% of the variability during transdermal nicotine treatment in the smoking cessation study. In contrast, 75 to 99% was accounted for by direct measurements of plasma clearances and systemic dose of nicotine in the pharmacokinetic study.
  
  
  CONCLUSIONS
  Plasma concentrations of nicotine and cotinine during transdermal nicotine treatment are poorly predicted by clinical history or baseline plasma concentrations. This is a result of inadequate characterisation of highly variable individual pharmacokinetic parameters and absorbed dose of nicotine. Considering the interindividual variability of plasma nicotine and cotinine concentrations together with the lack of clinical end-points for transdermal nicotine dosing, it seems logical to investigate the utility of a therapeutic drug monitoring approach for transdermal nicotine treatment-particularly for high dose regimens (> 22 mg per 24 hours).
authors.affiliation: UCSF Division of Clinical Pharmacology and Experimental Therapeutics 94143-0898, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Gourlay
authors.forename: N L
authors.initials: NL
authors.lastname: Benowitz
authors.forename: A
authors.initials: A
authors.lastname: Forbes
authors.forename: J J
authors.initials: JJ
authors.lastname: McNeil
mesh_terms: D000279:Administration, Cutaneous; D000293:Adolescent; D000328:Adult; D000368:Aged; D001315:Australia; D003367:Cotinine / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009538:Nicotine / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics*; D018722:Nicotinic Agonists / Q000097:blood / Q000493:pharmacokinetics*; D012907:Smoking / Q000097:blood*
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine; D003367:Cotinine