Inotropic agents may be classified according to their primary mechanism of action (Table 1), i. e. whether their action is dependent on or independent of cyclic adenosine monophosphate (cAMP) . The most important inotropic agents used clinically are cAMP-dependent: β-receptor agonists (e. g. epinephrine) and phosphodiesterase inhibitors (e. g. amrinone), which will be discussed in this chapter. Forskolin is a direct activator of adenylyl cyclase and therefore independent of the β-receptor. Dibutyryl cAMP is a cAMP analogue which directly stimulates calcium ingress. Both these agents are investigational and useful in defining mechanisms of inotropic action. Digoxin, which inhibits the cellular sodium-potassium pump, and calcium, the “third messenger” in all muscle contraction, act independently of cAMP. However, their usefulness as IV inotropic agents is limited by their toxic effects. Alpha-receptor agonists (e. g. norepinephrine) may have important inotropic activity in congestive cardiac failure where there has been down-regulation of the β-receptors.
KeywordsCardiopulmonary Bypass Adenylyl Cyclase Renal Blood Flow Inotropic Agent Inotropic Activity
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- 15.Rosenblum R, Tai A, Lawson D (1972) Dopamine in man: Cardio-renal hemodynamics in normotensive patients with heart disease. J Pharm Exp Therap 183: 256–263Google Scholar
- 20.Fowler MB, Alderman EL, Oesterle SN, et al (1984) Dobutamine and dopamine after cardiac surgery: Greater augmentation of myocardial blood flow with dobutamine. Circulation 70: 1103–1111Google Scholar
- 22.Hakim M, Foulds R, Latimer RD, English TA (1988) Dopexamine hydrochloride, a beta-2 adrenergic and dopaminergic agonist: Haemodynamic effects following cardiac surgery. Europ Heart J 9: 853–858Google Scholar
- 23.Smith GW, O’Connor SE (1988) A symposium: Focus on heart failure — Current experiences in basic research and clinical studies on dopexamine hydrochloride (Dopacard®): An introduction to the pharmacologic properties of Dopacard (dopexamine hydrochloride). Am J Cardiol 62: 9C - 17CPubMedCrossRefGoogle Scholar