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Mephentermine is thought to act as a releasing agent of norepinephrine and dopamine. [4] It is described as an indirectly acting sympathomimetic, cardiac stimulant, adrenergic, vasoconstrictor, antihypotensive agent, and psychostimulant. [1] [2] [8] [4] Its sympathomimetic effects are mediated by indirect activation of α-and β-adrenergic ...
Cardiotonic agents are typically employed as short-term and non-routine therapies for heart failure patients. [71] They are specifically reserved for those with contractile dysfunction in the left ventricles (lower chambers of the heart), low cardiac output, and low blood pressure, placing them at risk of inadequate organ perfusion. [72]
PDE3 inhibitors are indicated as inotropics for the therapy of acute heart failure if catecholamines are ineffective. [2] Well controlled studies have shown that these drugs generally increase mortality , [ 3 ] when used for the therapy of acute heart failure, so they have to be applied under close observation.
Negative inotropic agents decrease myocardial contractility and are used to decrease cardiac workload in conditions such as angina. While negative inotropism may precipitate or exacerbate heart failure in the short term, certain beta blockers (e.g. carvedilol , bisoprolol and metoprolol ) have been believed to reduce long-term morbidity and ...
Levosimendan is a calcium sensitizer — it increases the sensitivity of the heart to calcium, thus increasing cardiac contractility without a rise in intracellular calcium. Levosimendan exerts its positive inotropic effect by increasing calcium sensitivity of myocytes by binding to cardiac troponin C in a calcium
The mechanisms of sympathomimetic drugs can be direct-acting (direct interaction between drug and receptor), such as α-adrenergic agonists, β-adrenergic agonists, and dopaminergic agonists; or indirect-acting (interaction not between drug and receptor), such as MAOIs, COMT inhibitors, release stimulants, and reuptake inhibitors that increase the levels of endogenous catecholamines.
The effects of amrinone vary widely with species and experimental condition; therefore, its inotropic effects are variable. [3] A loss in sensitivity to phosphodiesterase 3 inhibitors, including amrinone, has been observed in end stage heart failure in humans; other treatment options may be more useful for improvement in these stages. [3]
Dobutamine is a direct-acting agent whose primary activity results from stimulation of the β 1-adrenoceptors of the heart, increasing contractility and cardiac output. Since it does not act on dopamine receptors to inhibit the release of norepinephrine (another α 1 agonist), dobutamine is less prone to induce hypertension than is dopamine .