title: Inotropic drugs and their mechanisms of action.
abstract: This report describes various old and new positive inotropic drugs with respect to their mechanisms of action. Drugs with established cardiotonic effects include cardiac glycosides, beta 1-adrenergic agents, glucagon, histamine and the methylxanthines. New agents discussed are prenalterol, beta 2- and alpha-adrenergic drugs, amrinone and sulmazole. Prenalterol is a beta 1-adrenergic agent. Beta 2-adrenergic drugs, amrinone and sulmazole, combine a positive inotropic and a vasodilator effect. The latter resemble theophylline and other methylxanthines in that they appear to act mainly as phosphodiesterase inhibitors with a subsequent increase in cyclic adenosine monophosphate (cAMP). The mechanism of the positive inotropic effect of alpha-adrenergic stimulating agents (for example, phenylephrine) is unknown. It is independent of the cAMP system and is not accompanied by changes in frequency.
mesh_terms: D000631:Aminopyridines / Q000494:pharmacology; D000676:Amrinone; D002118:Calcium / Q000378:metabolism; D002301:Cardiac Glycosides / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D011217:Practolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011294:Prenalterol; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013566:Sympathomimetics / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D002301:Cardiac Glycosides; D002316:Cardiotonic Agents; D007093:Imidazoles; D013566:Sympathomimetics; D014970:Xanthines; C008514:methylxanthine; D006632:Histamine; D005934:Glucagon; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; C029758:sulmazole; D000676:Amrinone; D011294:Prenalterol; D011217:Practolol; D002118:Calcium