Hemodynamic and regional blood flow response to piroximone (MDL 19,205) in dogs with congestive heart failure: a comparison with dobutamine.

This study compares the effects of piroximone (MDL 19,205), a new inotropic agent, with dobutamine in dogs with congestive heart failure. With dobutamine, (15 micrograms/kg/min) left ventricular (LV) dp/dt increased from 2220 +/- 215 (mean +/- S.E.M.) to 2815 +/- 280 mm Hg/sec and cardiac index increased from 2.9 +/- 0.2 to 3.7 +/- 0.4 liters/min/m2, whereas LV filling pressure was essentially unchanged (18.7 +/- 2.6-16.3 +/- 2.4 mm Hg). The hemodynamic effects of piroximone (50 micrograms/kg/min) were more pronounced. LV dp/dt increased from 2615 +/- 260 to 3760 +/- 410 mm Hg/sec and cardiac index from 3.0 +/- 0.1 to 4.4 +/- 0.6 liters/min/m2, whereas LV filling pressure decreased from 15.6 +/- 2.4 to 6.4 +/- 1.8 mm Hg (all P less than .05). Systemic vascular resistance index decreased from 2730 +/- 225 to 1905 +/- 256 dynes sec cm-5 m-2. Regional blood flow to the myocardium increased 48% with dobutamine and 24% with piroximone, whereas skeletal muscle flow increased 59% with dobutamine and 36% with piroximone. Renal blood flow remained unchanged with either drug. We conclude that piroximone is an inotropic agent with vasodilator properties that has an interesting hemodynamic profile somewhat similar to that of dobutamine but with the advantage of being orally active; therefore piroximone could be useful in the treatment of heart failure.