Excretion of technetium 99m hexakismethoxyisobutylisonitrile in milk

The amount of radioactivity excreted in breast milk following the administration of technetium 99m hexakismethoxyisobutylisonitrile (99mTc-IEAE) to a patient referred for cold spot myocardial scintigraphy was determined. During the first 24 h after administration, only 41.2 kBq99mTc (0.0084% of the injected dose) was excreted in 448 ml milk with the highest concentration of 0.49 kBq/ml in the first sample. The images obtained show a high concentration of99mTc-IEAE in the lactating breasts contrary to the very small percentage excreted in the milk. Comparison with various recommendations regarding nursing after administration of radiopharmaceuticals seems to indicate that the administration of99mTc-IEAE does not necessitate an interruption of breast-feeding.