title: N-isopropyl-4-[123I]iodoamphetamine (123I-IMP) products: a difference in radiochemical purity, unmetabolized fraction, and octanol extraction fraction in arterial blood and regional brain uptake in rats.
abstract: N-isopropyl-4-[123I]iodoamphetamine (123I-IMP) is a lipophilic compound utilized for cerebral blood flow (CBF) measurement with single photon emission computed tomography (SPECT). Two different 123I-IMP products (IMP(A) and IMP(B)) are commercially available. We examined the radiochemical purity, unmetabolized fraction, and octanol extraction fraction in arterial blood, and the regional brain uptake of IMP(A) and IMP(B) in a rat model. IMP(B) (96.4% +/- 0.08%, P < 0.05) showed significantly higher radiochemical purity than IMP(A) (95.5% +/- 0.20%). The mean unmetabolized fraction in arterial blood taken at 10 min after intravenous administration of IMP(B) (69.5% +/- 4.4%, P < 0.01) was significantly higher than that of IMP(A) (59.6% +/- 2.6%). The mean octanol extraction fraction of IMP(B) (75.0% +/- 1.3%, P < 0.01) was also significantly higher than that of IMP(A) (67.2% +/- 0.8%). The mean levels of radioactivity in arterial blood sampled at 10 min after injection and mean regional brain radioactivity (cerebral cortices, basal ganglia, brain stem, and cerebellum) at 10-12 min after injection were not significantly different between IMP(A) and IMP(B). The present study indicates differences in the radiochemical purity and the unmetabolized and octanol extraction fraction in arterial blood between the two commercially available 123I-IMP products. The appropriate octanol extraction fractions for IMP(A) and IMP(B) should be determined in humans and employed for quantitative CBF measurement in clinical SPECT.
authors: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. ykanai@tracer.med.osaka-u.ac.jp
authors: Yasukazu
authors: Y
authors: Kanai
authors: Shinji
authors: S
authors: Hasegawa
authors: Yasuyuki
authors: Y
authors: Kimura
authors: Naohiko
authors: N
authors: Oku
authors: Hiroshi
authors: H
authors: Ito
authors: Hiroshi
authors: H
authors: Fukuda
authors: Jun
authors: J
authors: Hatazawa
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply / Q000166:cytology / Q000000981:diagnostic imaging* / Q000378:metabolism*; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D020367:Iofetamine / Q000493:pharmacokinetics*; D008297:Male; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow; D012588:Scintillation Counting; D013997:Time Factors; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D020367:Iofetamine