ISSN 1066-3622, Radiochemistry, 2015, Vol. 57, No. 4, pp. 425–430. © Pleiades Publishing, Inc., 2015. Published in Russian in Radiokhimiya, 2015, Vol. 57, No. 4, pp. 361–365. 425 Radiodiagnosis of Peptic Ulcer with Technetium-99m Labeled Rabeprazole 1 M. H. Sanad* and I. T. Ibrahim Labeled Compounds Department, Radioisotopes Production and Radioactive Sources Division, Hot Laboratories Center, Atomic Energy Authority, P.O. Box 13759, Cairo, Egypt Received March 12, 2015 Abstract—Rabeprazole, antiulcer drug, was labeled with 99m Tc to obtain an agent for ulcer imaging. The radio- chemical yield of 99m Tc-rabeprazole reaches approximately 98.5 ± 0.4%.The optimum conditions are as fol- lows: pH 9, 50 μg of SnCl 2 ·2H 2 O, 30 min, and 3 mg of the substrate. 99m Tc-rabeprazole was stable for 6 h. Intra- venous biodistribution studies of 99m Tc-rabeprazole revealed high concentration in the stomach ulcer, reaching about 33.4% of the total injected dose at 30 min post injection. This concentration of 99m Tc-rabeprazole in stomach ulcer makes this agent promising for stomach ulcer imaging. Keywords: rabeprazole, technetium-99m, labeling, biodistribution, ulcer, imaging Rabeprazole sodium (see structure below) is so- dium salt of 2-[4-(3-methoxypropoxy)-3-methyl-2- pyridinyl]methylsulfinyl-1H-benzimidazole and is used as antiulcer agent [1] intended for treating acid- related gastrointestinal diseases such as reflux esopha- gitis and duodenal and gastric ulcers, and also for re- lieving heart pain [2, 3]. It is a proton pump inhibitor, which suppresses gastric acid secretion by specific inhibition of the gastric H + /K + /ATPase enzyme at the secretary surface of the gastric parietal cells [4]. Peptic ulcer is defined as mucosal erosions equal to or greater than 0.5 cm in an area of the gastrointestinal tract, which is usually acidic and thus extremely painful. As many as 80% of ulcers are associated with Helico- bacter pylori [5–7], a spiral-shaped bacterium that lives in the acidic environment of the stomach; how- ever, only 20% of those cases go to a doctor. Ulcers can also be caused or worsened by drugs such as aspi- rin and other nonsteroidal anti-inflammatories [8]. In vitro and in vivo diagnostic researches in nuclear medicine use radioisotopes and radiopharmaceuticals. Many tracers were used like 99m Tc, 153 Sm, and 89 Sr, etc. [9, 10]. Many compounds were subjected to labeling with these radioisotopes like MAG3, MDP, DTPA, etc. [11]. Many items should be under consideration for radioimaging, for example, radiopharmaceuticals developed for kidneys must focus on achieving high target selectivity and binding affinity, stability and slow metabolism in vivo, minimal nonspecific accu- mulation, and urinary excretion [12]. This study was aimed at labeling rabeprazole with 99m Tc, studying the factors that influence the labeling yield, and evaluating the labeled compound with chromatographic methods. The biodistribution of intravenously injected 99m Tc-ra- beprazole in normal mice and those with induced stomach ulcer was also studied. DOI: 10.1134/S1066362215040165 1 The text was submitted by the authors in English. Rabeprazole Chemicals and materials. Rabeprazole was a gift from Pharaonia Company for Pharmaceutics. All other chemicals were purchased from Merck and were of reagent grade. Double-distilled water was deoxygen- ated by purging with nitrogen gas. Apparatus. Well-type γ-scintillation counter: Sca- lar Ratemeter SR7 (Nuclear Enterprises, USA); pH meter: model 601 A digital ion analyzer (Orion Re- search, USA); ionization chamber: model CRC-15R EXPERIMENTAL