Technetium-99m DTPA inhalation scintigraphy in patients treated with fluoxetine and maprotiline: preliminary results

Drug-metabolising enzymatic activities have been detected in tracheobronchi olar, bronchiolar and alveolar regions in the lungs. Induction of phospholi pidosis by amine drugs such as clorphentermine has also been shown. This st udy aimed to investigate the effect of fluoxetine and maprotiline, which co ntain amine groups in their structure, on pulmonary epithelial membrane per meability. Twenty-seven patients (mean age 36 +/- 12 years) with various ps ychiatric problems, of whom 17 were treated with fluoxetine and 10 with map rotiline, were included in this study. Technetium-99m diethylene triamine p enta-acetic acid (DTPA) aerosol inhalation scintigraphy was performed befor e and after 4-6 weeks of therapy. Following the inhalation of 1450 MB Tc-99 m-DTPA for 3 min, lung images in a 64 x 64 matrix were obtained every minut e for 30 min. Regions of interest were drawn around the periphery of the lu ngs and on the major airways. Clearance half-times (T-1/2) were calculated by placing a mono-exponential fit on the curves. Penetration index (PI) was calculated on the first-minute image. There was no difference between the clearance rates of Tc-99m-DTPA before and after therapy for either the fluo xetine or the maprotiline group. After therapy, a significant decrease in P I was found in patients treated with fluoxetine (PI values before and after therapy: 0.53 +/- 0.03 and 0.49 +/- 0.05 respectively, P less than or equa l to 0.05). This finding might have been due to the induction of increased synaptic serotonin (5-HT) by fluoxetine, which acts by inhibiting the re-up take of 5-HT on presynaptic membranes. Bronchoconstriction of small and med ium airways may be caused by direct and indirect effects of 5-HT on smooth muscle contraction.