Evaluation of different formulations to label exogenous natural surfactant labeled with (99m-Tc-ENS): stability and toxicity studies

Exogenous natural surfactant (ENS) labeled with 99mTc (99mTc-ENS) is a new ventilatory agent for aerial lung scintigraphy. To develop a stable formulation of 99mTc-ENS to be routinely used in Nuclear Medicine Centers, the properties of two freeze-dried formulations (ENS + stannous chloride + gentisic acid and ENS + stannous chloride + ascorbic acid) and a control freeze-dried formulation of ENS were analyzed monthly for 12 months. Their physicochemical properties, labeling yields and biodistribution were adequate during this period. Since ENS + stannous chloride + gentisic acid formulation has the lowest dispersion of the biodistribution results, it was chosen for a future production of 99mTc-ENS. Acute toxicity of the chosen formulation demonstrates that the toxic dose is at least 1000 times higher than the diagnostic dose (Au)