Enhanced uptake of actinomycin D in the dog kidney by simultaneous injection of degradable starch microspheres into the renal artery.

Tritiated Actinomycin D and degradable starch microspheres were simultaneously injected into a renal artery in dogs. The spheres functioned to mechanically retard the washout of the drug from the kidney microcirculation. Degradation of the spheres by endogenous amylase resulted in the reestablishment of normal kidney blood flow within an hour after injection. Twenty-three per cent of the total amount of drug injected was retained in the kidney one hour after injection of the drug-sphere combination. When the same amount of the drug alone was selectively injected into a renal artery or given intravenously, 9% and 1.3% of the injected dose, respectively, was found in the kidney tissue one hour after injection. This procedure may be of benefit in the treatment of solid tumors, where the therapeutic ratio may be increased because of higher drug retention in the tumor tissue with a decreased availability of the drug for other sensitive tissues.