Radioiodinated paroxetine, a novel potential radiopharmaceutical for lung perfusion scan

Paroxetine (a selective serotonin reuptake inhibitor) was successfully labeled with I-125 via direct electrophilic substitution reaction at ambient temperature. The reaction parameters studied were paroxetine amount, CAT amount, pH of the reaction mixture, reaction temperature, reaction time and in vitro stability of I-125-paroxetine. I-125-paroxetine was obtained with a maximum labeling yield of 94 +/- 0.23% and in vitro stability up to 24 h. Biodistribution studies showed that maximum in vivo uptake of I-125-paroxetine in lungs was 27.89 +/- 1.03% injected activity/g tissue at 15 min post-injection and retention in lungs remained high up to 1 h, whereas the clearance from mice appeared to proceed mainly via the hepatobiliary pathway. I-125-paroxetine is not a blood product and so it is more safe than the currently available Tc-99m-macroaggregated albumin (Tc-99m-MAA), and its lung uptake is higher than that of the recently discovered Tc-99m(CO)(5)I and Tc-99m-DHPM. As a conclusion, radioiodinated paroxetine could be used as a novel radiopharmaceutical for lung perfusion scan safer than the currently available Tc-99m-MAA and more potential than the recently discovered Tc-99m(CO)(5)I and Tc-99m-DHPM.