SC-5233, also known as 6,7-dihydrocanrenone or 20-spirox-4-ene-3,20-dione, is a synthetic, steroidal antimineralocorticoid of the spirolactone group which was developed by G. D. Searle & Company in the 1950s but was never marketed. It was the first synthetic antagonist of the mineralocorticoid receptor to have been identified and tested in humans. The drug was found to lack appreciable oral bioavailability and to be of low potency when administered parenterally, but it nonetheless produced a mild diuretic effect in patients with congestive heart failure. SC-8109, the 19-nor (19-demethyl) analogue, was developed and found to have improved oral bioavailability and potency, but still had low potency. Spironolactone (SC-9420; Aldactone) followed and had both good oral bioavailability and poten