4-Iodoantipyrine was synthesised from phenazone, labeled with123I and administered to cells in culture. 4-[123I]iodoantipyrine carries the radionuclide across the cell membrane allowing one to study the biological effects of the very
short ranged Auger electrons emitted by this isotope. The formulation used to prepare this compound proves to be free of reagents
that may have an adverse effect on the mitotic activity of cells in culture. By observing micronuclei frequencies in human
lymphocytes and CHO-K1 cells the high-LET characteristics of Auger electrons could be demonstrated. Compared to extracellular
disintegrations from [123I]NaI and123I-human serum albumin, a substantial reduction in the variation in radiosensitivity of these cell types was noted when treated
with 4-[123I] iodoantipyrine.