Preparation and quality control of 99m Tc-MDPA

Since the early 1970s a number of 99mTc-phosphate compounds have been introduced for bone imaging. The three extensively studies diphosphonates are: 1-hydroxyethylidene diphosphonate (HEDP), methylene diphosphonate (MDP) and hydroxymethylene diphosphonate (HMDP or HDP) of which MDP and HDP are most commonly used in nuclear medicine. This report describes the routine production and quality control of MDP ('multidose') at IPEN-CNEN/SP, in lyophilized form for labeled with high activities of 99mTc (9,250 MBq). The process was done under vacuum and low temperature in Super Modulyo -'Edwards' lyophilizator and each lyophilized vial contains: 5.0 mg of MDP; 1.0 mg SnCl2.H2O; 0.1mg ascorbic acid and 20.0 mg sodium pyrophosphate at pH = 6.0. The radiochemical purity was determined by thin layer chromatography system in Whatman 3MM paper (1 x 8 cm), using acetone and saline (0.9% NaCl) as solvents, respectively. Sterility and pyrogen tests were performed by the microbiology procedures outlined in the pharmacopoeias and by the 'in-vitro' Limulus test, respectively. Biological distribution in Wistar rats was evaluated in different organs (% dose / organ). The method was validated for routine production at Radiopharmacy Center, the radiochemical purities of 99m Tc-MDP ('multidose') was > 95%. The biological distribution in rats showed high uptake in bone tissue, and low activities in thyroid, liver and stomach. Sterility and pyrogen tests were negative in all the delivered lyophilized vials. (author)