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Isoprenaline has positive inotropic and chronotropic effects on the heart. β 2-Adrenergic receptor stimulation in arteriolar smooth muscle induces vasodilation. Its inotropic and chronotropic effects elevate systolic blood pressure, while its vasodilatory effects tend to lower diastolic blood pressure.
[74] Isoprenaline also exerted marked positive chronotropic and inotropic effects. Boehringer introduced it for use in asthma in 1940. After the war it became available to Germany's former enemies and over the years was traded under about 50 names.
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.
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 ...
increase cardiac output by increasing heart rate (positive chronotropic effect), conduction velocity (positive dromotropic effect), stroke volume (by enhancing contractility – positive inotropic effect), and rate of relaxation of the myocardium, by increasing calcium ion sequestration rate (positive lusitropic effect), which aids in ...
Epinephrine (adrenaline). Activation of β 1 receptors induces positive inotropic, chronotropic output of the cardiac muscle, leading to increased heart rate and blood pressure, secretion of ghrelin from the stomach, and renin release from the kidneys.
Isoprenaline has higher affinity for β 1 than adrenaline, which, in turn, binds with higher affinity than noradrenaline at physiologic concentrations. As ADRB-1 increases cardiac output, selective agonists clinically function as potential treatments for heart failure. Selective agonists to the beta-1 receptor are:
Isoprenaline (non-selective) Norepinephrine reuptake inhibitors , like atomoxetine , methylphenidate , and cocaine , as well as norepinephrine releasing agents , like amphetamine , ephedrine , pseudoephedrine , and phenylpropanolamine , indirectly activate β 1 -adrenergic receptors (as well as other adrenergic receptors) by increasing ...