Relationship between plasma and oral fluid nicotine concentrations in humans: a pilot study

The relationship between plasma and oral fluid concentrations of nicotine after infusion at varying times was investigated. Five healthy human volunteers were administered 0, 0.75, and 1.5 mg nicotine as 0.5-, 1.0-, 2.5-, and 5-minute infusions. Blood and oral fluid were collected before drug administration and for 4 hours thereafter. Nicotine concentrations were determined by HPLC using a limit of quantification of 1 ng/mL. Plasma nicotine concentrations were dose related. Peak plasma concentrations (mean+/-SD) at the 4 infusion times were 14.1+/-5.5, 11.8+/-5.3, 12.8+/-1.9, and 11.5+/-4.0 ng/mL (N=5) after the 0.75-mg dose and 26.3+/-11.7, 19.3+/-12.8, 24.54+/-10.4, and 19.02+/-6.5 ng/mL after the 1.5-mg dose. In general, the highest peak concentration occurred at the shortest infusion time at each dose. Peak nicotine oral fluid concentrations (mean+/-SD) at the 4 infusion times of 22.4+/-29.1, 22.64+/-29.9, 19.1+/-13.5, and 49.1+/-31.7 ng/mL (n=5) after the low dose and 35.8+/-21.1, 26.0+/-7.7, 33.3+/-28.8, and 104.0+/-68.9 ng/mL, after the 1.5 mg dose. The highest oral fluid concentration of nicotine occurred at the longest infusion time at each dose. Oral fluid/plasma were >1 for up to 60 minutes after the low dose and 120 minutes after the high dose. There was no correlation between plasma and oral fluid nicotine concentrations.