REGIONAL DEPOSITION OF INHALED C-11 NICOTINE VAPOR IN THE HUMAN AIRWAY AS VISUALIZED BY POSITRON EMISSION TOMOGRAPHY

The deposition of C-11-nicotine in the respiratory tract from a nicotine vapor inhaler was studied by means of positron emission tomography (PET) in an intrasubject comparison of six healthy smokers using two modes of inhalation: one with shallow, frequent inhalations (''buccal mode'') and one with deep inhalations (''pulmonary mode''). An average of 15% of the radioactivity was released from the vapor inhaler after 5 minutes of inhalation, Approximately 45% of the dose released was found in the oral cavity, A significant amount of radioactivity, 10%, was observed in the esophagus, suggesting transfer of a major fraction of the dose to the stomach, Only a minor fraction, 5%, was found in the lungs, followed by 2% in the bronchi and 1% in the trachea. The deposition in the oral cavity closely followed a linear pattern during the 5 minutes of inhalation and was followed by a rapid elimination from the oral cavity, with an average half-life of 18 minutes. Only 8% of the dose released remained in the oral cavity 45 minutes after the end of inhalation, On the other hand, the dose fraction of about 14% distributed into the body tissue compartment at the end of inhalation had risen to 60% at that late time point. No statistically or clinically important differences were observed between the buccal and the pulmonary mode of inhalation in either deposition pattern or elimination rates.