Technetium ⁹⁹ᵐTc phytate Other names: Technetium TC-99M phytate

After administered intravenously ^99mTc-phytate forms a microdisperse system (colloid) with calcium ions of the blood. The cells of the liver and the spleen, the Kupffer-cells and the reticuloendothelial system extract that system from the blood (phagocytosis). 90-95% of the activity appears in the liver. Further 5-10% is deposited in the spleen and the bone marrow. The colloid leaves the liver in the way of slow degradation and hydrolysation of the micro-particles.

In case of impaired liver function the bone marrow radioactivity is increased and some activity appears in the lungs. However, diffuse liver diseases result in an increased spleen activity.

^99mTc-phytate introduced intravenously leaves the bloodstream in two parallel processes described by two exponential curves:

Fast process T_1/2 = 2.4-7 min

Slow process T_1/2 = 69-105 min

The fast process is the result of the operation of the reticuloendothelial system.

The liver uptake is quick, it can be observed even some minutes after administration. After thirty minutes 90% of the radioactivity is accumulated in the liver. However, excretion from the liver is extremely slow.

Acute toxicity study of rats showed no clinical symptoms up to 4 mg/kg of body weight. Quantity of the administered ^99mTc-Technephyte, if complying with the recommendations, is not less than 2.5 mg and not more than 5.0 mg. Calculated on an average 70 kg of bodyweight the smallest and the greatest quantities are equivalent to 0.9 and 1.8% of the no observed effect level, respectively.

Thus, the use of technetium ^99mTc phytate considered safe.

Further advantage of the technetium ^99mTc phytate is that the activity of [^99mTc] pertechnetate in the range of 0.8 –1.6 GBq does not affect the radiochemical purity of the preparation. Quantity of radiochemical impurities is always less than 10%, therefore the kit is safe from the point of view of labelling.