Cigarette smoking as a risk for cardiovascular disease V: Biochemical parameters with increased and decreased nicotine content cigarettes.

Cigarette smokers were assessed for customary smoking behavior and then were assigned a cigarette which was 0.4 mg higher or lower in nicotine and after 4 weeks, were returned to their customary brand. Biochemical indices of smoking behavior including blood carboxyhemoglobin (COHb), plasma nicotine, cotinine and thiocyanate (-SCN) were measured every 2 weeks. When nicotine availability was increased, smokers received an increased nicotine bolus per puff as determined by plasma nicotine and did not alter smoking topography or cigarettes per day. Over the 4 weeks, plasma cotinine increased without corresponding increases in COHb and -SCN. The return to standard brand resulted in declining cotinine levels but increasing COHb and -SCN, suggesting altered inhalation patterns. In smokers switched to a low yield cigarette, there was a decrease in the nicotine obtained per cigarette followed by a steady rise in plasma cotinine, -SCN and blood COHb over the 4-week period. A positive correlation was observed between cotinine and the gas phase constituents during the change to lower yield and back to standard brand cigarettes. These results indicate that cigarette smokers compensate for decreased nicotine yield with concomitant increases in gas phase components. In addition, increased nicotine availability results in an increased body burden of nicotine and "tar," but not gas phase constituents. The relative risks of cardiovascular disease under these two situations, which increase exposure to nicotine or gas phase components, deserve careful consideration.