Technetium-99m-tetrofosmin: retention of nitrogen atmosphere in kit vial as a cause of poor quality material

Technetium-99m (Tc-99(m))-tetrofosmin was prepared using four different rec onstitution methods. The radiochemical purity (RCP) of these products was a ssessed 8 h later using thin layer chromatography (TLC). Material produced using the original method supplied by the manufacturer and using an newer m ethod, which involves the use of a vent needle and the addition of air, had acceptable RCP (mean +/- SD 94.2+/-1.1% and 94.7+/-1.7%, respectively) and similar chromatograms. In addition, both products showed good clinical eff icacy and exhibited normal biodistribution behaviour. Preparing Tc-99(m)-te trofosmin using the two other methods, one using a high radioactive concent ration and the other maintaining the nitrogen content of the kit vial, gave rise to chromatograms with reduced RCP (63.5+/-10.9% and 61.9+/-7.6%, resp ectively) and greater levels of impurities. Although neither of these last two preparations was used clinically, we suggest that reports of poor quali ty images may be the result of administration of materials similar to these . Results for the high radioactive concentration method were as expected an d are consistent with the restrictions imposed by the manufacturer. However , results using the last method are surprising and would suggest that the p roduction of good quality Tc-99(m)-tetrofosmin is dependent on the quantity of nitrogen in the kit vial. We believe that the amount of nitrogen remove d from the kit vial during the process of reconstitution is critical. Lf to o much nitrogen is present this will result in poor quality material. In pr actice it is conceivable that there could be occasions when insufficient ni trogen is removed when following the manufacturer's original guidance, ther eby leading to low RCP material. To ensure adequate nitrogen is removed dur ing reconstitution, adoption of the manufacturer's revised method, involvin g the deliberate introduction of air, is therefore appropriate. ((C) 2000 L ippincott Williams & Wilkins).