Canrenoate disposition in dogs. Tissue distribution and elimination

The metabolism and tissue distribution of intravenously administered C14-canrenoate-potassium (CR-K) was studied at various time intervals in 10 dogs. After a rapid decline of total radioactivity immediately after injection, the elimination in plasma occurred in two distinct phases with half-lives of 6.8 and 23.6 h. Canrenoate was rapidly converted to lipid- and water-soluble metabolites which were separated by thin-layer chromatography. Most tissues showed similar concentrations of total radioactivity as plasma. An accumulation of radioactivity per g wet weight was detected in the adrenal glands and fat tissue as well as in the metabolic and excretory organs but not in the heart. Taking into consideration that skeletal muscle, fat tissue and liver constitute about 64% of the body weight, it is obvious that the main part of total radioactivity was present in these tissues. In contrast to plasma, urine and feces, where various metabolites could be analysed, the bulk of radioactivity in tissues is represented by canrenone. Thus, the estimation of the parent compound and its metabolites in plasma, urine and feces does not allow final conclusions about the active substance in various tissues. Within 72 h 47% of the dose was recovered in urine and 49% in feces.