131 I-trazodone: preparation, quality control and in vivo biodistribution study by intranasal and intravenous routes as a hopeful brain imaging radiopharmaceutical.

OBJECTIVES: The preparation of 131 I-trazodone hydrochloride and its biological evaluation as a promising brain imaging radiopharmaceutical using two routes of administration.

MATERIAL AND METHODS: Trazodone (TZ) was radiolabelled with 131 I using direct electrophilic substitution, and different factors affecting labelling yield were studied. Quality control of 131 I-TZ was carried out using ascending paper chromatography, paper electrophoresis, and high pressure liquid chromatography (HPLC). In vivo biodistribution of 131 I-TZ was evaluated in Swiss albino mice using 3 methods: intravenous 131 I-TZ solution (IVS), intranasal 131 I-TZ solution (INS), and intranasal 131 I-TZ microemulsion (INME).

RESULTS: Optimum labelling yield of 91.23±2.12% was obtained with in vitro stability of 131 I-TZ up to 6h at room temperature. The biodistribution results showed a notably higher and sustained brain uptake for INME compared to IVS and INS at all time intervals. In addition, heart and blood uptake levels for INME were lower than those for IV solution which, in turn, could decrease the systemic side effects of trazodone. Also, the 131 I-trazodone INME brain uptake of 6.7±0.5%ID/g was higher than that of 99m Tc-ECD and 99m Tc-HMPAO (radiopharmaceuticals currently used for brain imaging).

CONCLUSION: 131/123 I-trazodone formulated as INME could be used as a promising radiopharmaceutical for brain imaging.