Mechanism of cardiovascular actions of heptanolamines

It has been suggested that heptaminol and methylheptaminol should be used as myocardial stimulants because they have cardiotonic actions similar to those of cardiac glycosides. However, as these aliphatic amines show definite sympathomimetic effects, the mechanism of their actions on the heart was investigated, in order to determine whether digitalis-like properties are involved in these effects. The pattern of pharmacological actions of heptaminol and methylheptaminol was compared with that of catechol amines, tyramine and k-strophanthin. The influence of atropine, hexamethonium, cocaine and reserpine was also investigated. The results show that both heptanolamines have a long-lasting cardiostimulant action which is abolished by cocaine and absent in reserpine pretreated animals. The pharmacological activity of these drugs may be entirely attributed to an indirect sympathomimetic action of the tyramine type, probably due to release of endogenous catechol amines. None of the experimental findings is consistent with the alleged digitalis-like action of these compounds.