RADIOCHEMICAL AND RADIOPHARMACOLOGICAL PROPERTIES OF PIROCARBOTRAT AND OTHER LABELED CHARCOAL DISPERSIONS - COMPARATIVE-STUDIES IN RATS WITH NMU-INDUCED MAMMARY-TUMORS

The purpose of this work is to study the physicochemical properties of Pirocarbotrat to explain its radiopharmacological behavior. We also s tudied a mixture of charcoal plus chromic [P-32]phosphate and charcoal plus sodium [P-32]orthophosphate only for comparative purposes. The r esults show that the mean diameter of the Pirocarbotrat particles was 2.5 mu m with an homogeneous distribution, while the other products sh ow an heterogeneous distribution of the particle sizes, with a mean si ze diameter between 0.5 and 0.9 mu m. Hydrolysis studies with a soluti on of 0.1 N HCl and with sulfochromic mixture revealed that in Pirocar botrat the P-32 is strongly bound to the charcoal particles. Bioelimin ation studies of Pirocarbotrat show that the total eliminated activity was 12.70 +/- 3.90%, with a higher amount in urine (8.30 +/- 1.80%) t han in feces (4.40 +/- 3.50%). When biodistribution studies of Pirocar botrat were carried out, we found that the 84.50 +/- 2.60% of the acti vity remained in the tumor with almost null irradiation of the other o rgans under study. When therapeutic action was evaluated, we observed that the percentage of tumor regression was 78.3% for the tumors injec ted with Pirocarbotrat. The other dispersions under study showed diffe rent behaviors with high activity percentages distributed throughout t he organism. These studies demonstrate that Pirocarbotrat has the best radiopharmacological properties to ensure irradiation of the tumor wi th the least concomitant irradiation of surroundings or other organs o r tissues. (C) 1998 Elsevier Science Inc.