Novel radioiodinated sibutramine and fluoxetine as models for brain imaging

Brain imaging is a process which allows scientists and physicians to view and monitor the areas of the brain which allow diagnosis and following up different abnormalities in the brain. The aim of this study was to develop potential radiopharmaceuticals for the non-invasive brain imaging. Sibutramine and fluoxetine (two drugs that have the ability to cross blood–brain barrier) were successfully labeled with ¹²⁵I via direct electrophilic substitution reaction at ambient temperature. The reaction parameters studied were substrate concentration, oxidizing agent concentration, pH of the reaction mixture, reaction temperature, reaction time and in vitro stability of the iodocompounds. The iodocompounds gave maximum labeling yield of 92 ± 2.77 and 93 ± 2.1%, respectively, and maintained stability throughout working period (24 h). Biodistribution studies showed that maximum in vivo uptake of the iodocompounds in the brain was 5.7 ± 0.19 and 6.14 ± 0.26% injected activity/g tissue organ, respectively, at 15 and 5 min post-injection, whereas the clearance from the mice appeared to proceed via the hepatobiliary pathway. Brain uptake of ¹²⁵I-sibutramine and ¹²⁵I-fluoxetine is higher than that of ^99mTc-ECD and ^99mTc-HMPAO (currently used radiopharmaceuticals for brain imaging) and so radioiodinated sibutramine and fluoxetine could be used instead of ^99mTc-ECD and ^99mTc-HMPAO for brain SPECT.