Enoximone is an imidazole derivative which proved to be a selective inhibitor of the isoenzymes III/IV of the cAMP-specific phosphodiesterase. It has been shown in various experimental models that the drug exerts both positive inotropic and vasodilating properties which can be attributed to the proposed mode of action. A marked dose-dependent improvement in left ventricular pump performance was observed, with only minor changes in heart rate or systemic blood pressure, if enoximone was administered as i.v. -bolus to patients with moderate to severe congestive heart failure. These effects coincided with vasodilatory effects as determined by decreases in systemic vascular resistance and pulmonary capillary wedge pressure. Enoximone is eliminated by intensive metabolism, predominantly in the liver, with enoximone sulfoxide being the major metabolite in man. Enoximone exhibits a marked firstpass metabolism following oral administration. There is evidence in the literature that the metabolism can be saturated either during long-term administration or by increasing the dose of enoximone. In experimental settings, the metabolite exerts weak positive inotropic effects, too, and reconversion to the parent compound enoximone has been demonstrated in addition. The half-life of elimination of enoximone seems to be about 1 h in healthy volunteers and approximately 3 to 7 h in patients with congestive heart failure, with marked inter-individual differences. In patients with renal failure mainly enoximone sulfoxide accumulates in plasma depending on the degree of renal impairment. The elimination of enoximone seems to be impaired in these patients, too, which might be caused by enhanced reconversion due to the high plasma concentrations of the metabolite.(ABSTRACT TRUNCATED AT 250 WORDS)