Dynamics of brain nicotine accumulation after inhalation of a single puff of cigarette smoke

Abstract

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Objectives: To test hypotheses that the concentration of nicotine in the brain reaches the maximum within several seconds of each puff of cigarette smoke and rapidly washes out before the next puff.

Methods: PET scans of the head and chest of thirteen dependent smokers were acquired in two sessions. Subjects were imaged over 10 minutes after inhalation of a single puff from a Quest 1 research cigarette containing 370 MBq of [¹¹C]-nicotine.

Results: The maximum concentration of brain [¹¹C]-nicotine was observed at 290 ± 30 sec after inhalation and calculated to be 4.9 ± 0.6 % of the inhaled dose per kg brain tissue. The time (T_1/2) to reach 50% of the maximum [¹¹C]-nicotine concentration was 33 ± 4 sec. The T_1/2 values for washout of [¹¹C]-nicotine from the lungs (on average 89 ± 18 sec) strongly correlated with the T_1/2 of accumulation in the brain (r = 0.90, P < 0.0001).

Conclusions: The accumulation of nicotine in the brain is a moderately slow process and dependent on the slow washout of nicotine from the lungs. The results suggest that smoking an entire cigarette (inter-puff interval ca. 30 sec) will gradually increase the concentration of free brain nicotine to a maximum value of ca. 150 nM.

Research Support: Philip Morris USA