Relationship between positive inotropic action and blood levels of denopamine in cats.

The relationship between the positive inotropic action and blood levels of (-)-(R)-1-(p-hydroxyphenyl)-2-[(3,4-dimethoxyphenethyl)amino]ethanol (denopamine, TA-064) was studied after intraduodenal administration of 3H-denopamine (100 micrograms/kg) in cats. The increase in cardiac contractile force attained the peak (about 100% increase) 15 min after the administration and the effect persisted for over 90 min. The blood levels of denopamine also reached the peak at 15 min with a concentration of 20 ng/ml and decreased gradually thereafter. Thus, it was indicated that the time courses of the increase in cardiac contractile force were closely related to those of blood levels of the drug. Furthermore, denopamine was distributed to the liver, kidney, parotid gland and heart, followed by being excreted into the urine and bile mostly as metabolites.