Plasma and urine changes after smoking different brands of cigarettes.

Concentrations of nicotine, cotinine, and carboxyhemoglobin (COHb) were measured in the plasma of subjects who smoked 1 cigarette of each of 10 different brands and then smoked 1 brand for 2 wk. There were higher COHb levels in smokers of low CO-yield cigarettes, whereas the rise in nicotine after 1 cigarette of each of the different brands was related to its nicotine content. Assay of urinary and plasma cotinine levels in smokers smoking brands with different nicotine content showed that smokers adjusted their smoking habits to maintain a constant level of cotinine. This self-titration of nicotine by the smoker may pose a health hazard even with relatively low nicotine cigarettes.