Nicotine absorption after pulmonary instillation.
Levels of nicotine in plasma were determined by gas chromatography in eight mongrel dogs after instillation of 0.5 mg of nicotine in 100 microL of normal saline at three levels of the tracheobronchial tree: the trachea, a subsegmental bronchus of the right middle lobe, and a subpleural location of the right middle lobe ("distal"). An equivalent dose was given intravenously (iv). Peak of nicotine concentrations in plasma were significantly lower after instillation at the trachea (11.5 +/- 4.4 ng/mL) and the subsegmental bronchus (18.2 +/- 5.0 ng/mL) than after an iv dose (30.3 +/- 10.7 ng/mL); p < 0.05 for each comparison. In addition, the peak concentration after instillation at the trachea was significantly lower than that after instillation at the distal site (22.1 +/- 6.2 ng/mL, p < 0.05). Time to peak concentration was significantly longer after tracheal instillation (5.3 +/- 3.0 min) than after subsegmental instillation (2.0 +/- 0.0 min) or iv infusion (2.0 +/- 0.0 min); p < 0.05 for each comparison. Total drug absorbed, half-life, and clearance were equivalent from all four sites. This study demonstrated that quantitative absorption of nicotine from the described lung sites is equivalent to that after an iv dose, with slower absorption and lower peak concentrations from the tracheal site.