Pharmacokinetics of the new aldosterone antagonist, spirorenone, in healthy volunteers after single and repeated daily doses.

The plasma concentrations of spirorenone in two groups of male volunteers have been determined after single and 14 daily doses of spirorenone 10 and 40 mg. Independent of the dose and pretreatment, spirorenone was absorbed with a half-life of 20-30 min, achieving maximum concentrations of about 100 ng/ml (10 mg) and 260 ng/ml (40 mg) after 1-2 h. Disposition of the parent drug was biphasic with half-lives of 50-60 min (distribution) and 5-6 h (elimination). Neither significant accumulation nor enzyme induction were observed after prolonged treatment. In one test subject given spirorenone 40 mg, the concentration of an active metabolite, 1,2-dihydrospirorenone, was measured. This compound accumulated considerably after multiple dosing and the area under the plasma concentration-time curve increased from 16 to 52% relative to that of spirorenone itself.