Technetium (99mTc) labelled EDDA/HYNIC-TOC binds with high affinity to somatostatin receptor subtypes 2 and 5, also to subtype 3 but with lesser affinity.
At the chemical concentrations used for diagnostic examinations 99mTcEDDA/HYNIC-TOC does not appear to have any pharmacodynamic activity.
After intravenous administration, 99mTc-EDDA/HYNIC-TOC is rapidly eliminated from the blood. Already after 10 minutes, accumulation of the 99mTc-EDDA/HYNICTOC is seen in the main organs, i.e. liver, spleen and kidneys as well as in tumours expressing somatostatin receptors.
Maximal values of the tumour/background ratio are observed at 4 hours after injection. Cancer lesions are still visible after 24 hours. Slight excretion by the alimentary tract is observed in late images.
The activity is excreted mainly by the renal route with a small contribution of hepatic excretion. 99mTc-EDDA/HYNIC-TOC is rapidly eliminated from the blood. The activity accumulated in the blood cells is below 5% regardless of time after injection.
In studies performed in mice and rats no effects of acute toxicity at dose level of 40 µg/kg bodyweight have been found. Toxicity with repeated administration of 99mTc-EDDA/HYNIC-TOC was not tested. This agent is not intended for regular or continuous administration.
Mutagenicity studies performed in a bacterial reverse mutation assay showed no 99mTc-EDDA/HYNIC-TOC induced gene mutations.
Long-term carcinogenicity studies have not been carried out.
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