Effects of cigarette smoking on iodine 123 N-isopropyl-p-iodoamphetamine clearance from the lung.

Iodine 123 N-isopropyl-p-iodoamphetamine (123I-IMP), originally developed as a brain scanning agent, is also taken up by the lung. To evaluate the effects of cigarette smoking on the kinetics of IMP in the lung, we studied 123I-IMP clearance from the lung in 18 volunteers (8 non-smokers and 10 smokers). After the injection of 111 MBq of 123I-IMP into the medial cubital vein, the time-activity curve for 60 min and the regional activity using 1 frame per minute and a 64 x 64 matrix were obtained. The 123I-IMP clearance curve was described as follows: C(t) = A1e-k1t + A2e-k2t (A1, A2: intercepts, and k1, k2: slopes of the exponential components). 123I-IMP clearance was delayed in smokers, and k2 was smaller in smokers. Also, a correlation between k1, k2, and the number of cigarettes smoked per day was found (r = -0.65, r = -0.74, respectively, P less than 0.01). In conclusion, this study suggests that the delayed clearance and retention of 123I-IMP in the lung indicate lung metabolic disorders due to cigarette smoking.