The removal of 14 C-edrophonium from the circulation

The clearance of (14)C-edrophonium from plasma was studied in the rat. Distribution studies showed that 5 min after intravenous injection of the drug, more than half the dose was present in the liver and the kidneys. The concentration in these organs was approximately 20 times the level in other tissues. The plasma concentration of (14)C-edrophonium was invariably expressed as the sum of two exponential terms, suggesting that the drug may return to the circulation from other tissues as the plasma level falls.