783 



OGfRETTE YIELDS AND SMOI<£ BlOAVAlLABlUi » 



J»? 



' >• 

 m 

 lb 



M 



PU5m« Cotinln* 



11 IJ U L4 IJ 1J 



FTC NIcotkM (m^ci») 



Fig. 3. Trends of mean p(asma nicotine, cotininc, and nicotine to cotinine conversioa me (/«} as a 

 funcuon of FTC nKxdne ykW of cigarettes smoked (95% confidence intervaJj). 



Such data open ib< possibility of estimating individual metabolic conversion rates (I- 

 K%) of nicotine to cotininc: 



I-K* = lOO«P(Cot)s.s.« Jt^» Ki«[l - (0.5)'*'*1/(I-MNIC) 



where P(Cot)s.s. is the plasma cotinine level measured in late afternoon at or near 

 steady state for each individual, H^ is the individual weight, V^ = 1 !00 mlAj is the 

 mean volume of distribution of cotininc, I-MNIC is the mean individual mtake of 

 nicotine per cigarette as previously defined, dt = 900 min/(CPD - I) is the individual 

 mean interval between cigarettes smoked, and h = 900 min is the mean tenniaal half- 

 life for plasma cocinine (8). The estimated mean conversion rate K% is arooad 45%; 

 this value is obviously sensitive to the choice of parametric determinants, bat not so 

 for the slope of the relationship, which appears independent of cigarette nicodse yield, 

 as Fig. 3 shows. 



