Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1323099 (sympathomimetic)
 2,957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ibopamine is an orally active derivative of dopamine (DA) which metabolizes to its active form, epinine. Epinine is one of the few catecholamines that possess dopaminergic--DA1 and DA2--activity, alpha 1, alpha 2, beta 1, and beta 2 activity, with indirect sympathomimetic action of dopamine. Ibopamine increased positive dP/dt, stroke volume, aortic blood flow, renal blood flow, and diuresis in animals. In healthy volunteers and patients with heart failure, a single oral dose of ibopamine showed primary vasodilating action (postsynaptic DA1 activity and presynaptic DA2 activity). Following a single oral dose of 100 or 200 mg of ibopamine, the plasma concentration of epinine reached its peak within 30 minutes, and declined rapidly so that concentration was not detectable after 1.5-3 hours. Pharmacokinetics and hemodynamic effects in congestive heart failure patients are also discussed.
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PMID:Clinical pharmacology of ibopamine. 167 50

Mechanisms contributing to the increments in heart rate (HR) and cardiac contractile force (CCF) produced by dopexamine (DPX) were studied in anesthetized dogs. Intravenous infusions of DPX (4.0 micrograms/kg/min) produced increments in HR, CCF and renal blood flow and decrements in mean arterial pressure (MAP). The sequential administration of atenolol (0.5 mg/kg i.v.) administered at a dose selective for beta-1 adrenoceptors, propranolol (2.5 mg/kg i.v.) and the DA1 dopamine receptor antagonist, SCH 23390 (10 micrograms/kg i.v.) blocked the DPX-induced changes in HR, CCF, MAP and renal blood flow, respectively. After ganglionic blockade, the increments in HR and CCF produced by DPX (4.0 and 16.0 micrograms/kg i.v.) were reduced 90 and 76%, respectively, with little or no change in its hypotensive effect. In separate dogs, administration of the beta-2 adrenoceptor agonist salbutamol (0.55 microgram/kg i.v.) produced a comparable decrement in MAP but smaller increments in HR and CCF than produced by DPX (16.0 micrograms/kg i.v.). DPX (64 micrograms/kg i.v.) also produced greater increments in HR during cardioaccelerator nerve stimulation (1 Hz, 0.5 msec, supramaximal voltage) than before nerve stimulation. Therefore, we tested the effect of DPX (1.0, 4.0 and 8.0 micrograms/kg/min i.v.) on the increments in HR, CCF and MAP produced by norepinephrine (0.25 microgram/kg i.v.) and the indirect acting sympathomimetic amine, tyramine (60 micrograms/kg i.v.). DPX potentiated the increments in HR, CCF and MAP produced by norepinephrine and suppressed those produced by tyramine. Thus, the positive inotropic and chronotropic effects of DPX in the intact dog are due primarily to baroreceptor-mediated stimulation and inhibition of neuronal uptake of norepinephrine.
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PMID:Mechanisms mediating the positive inotropic and chronotropic changes induced by dopexamine in the anesthetized dog. 288 76

We have studied the contribution of neuronal and postjunctional dopamine (DA) receptors and of the DA1 and DA2 receptor subtypes to the blood pressure effects of DA and bromocriptine in the rabbit. The norepinephrine release rate, i.e., the rate of entry of endogenous norepinephrine into the plasma, was derived from the plasma level of endogenous norepinephrine and the plasma [3H]norepinephrine clearance. Bromocriptine (40 micrograms kg-1) lowered the norepinephrine release rate and the arterial blood pressure both in anesthetized rabbits and in pithed rabbits with electrically stimulated sympathetic outflow. These effects were antagonized by the selective DA2 antagonist domperidone but not by the selective DA1 antagonist SCH 23390. DA (10-160 micrograms kg-1 min-1) dose-dependently increased the norepinephrine release rate and caused only transient hypotension in anesthetized rabbits. However, after treatment with desipramine, DA did not change the norepinephrine release rate and produced a persistent fall in blood pressure. When DA and domperidone were given simultaneously to desipramine-treated rabbits, the hypotensive effect of DA was unchanged, but now DA increased the norepinephrine release rate. When DA and SCH 23390 were given simultaneously to desipramine-treated rabbits, DA failed to lower blood pressure and decreased the norepinephrine release rate. Propranolol did not change the effects of DA in desipramine-treated rabbits. These results suggest that bromocriptine decreases blood pressure by activating ganglionic and/or prejunctional, inhibitory DA2 receptors in the peripheral sympathetic nervous system. DA also activates these receptors, but in addition releases norepinephrine in the manner of an indirectly acting sympathomimetic amine and activates postjunctional vascular DA1 receptors, and the latter seems to be the main component in DA-induced hypotension.
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PMID:Neuronal and postjunctional components in the blood pressure effects of dopamine and bromocriptine in rabbits. 299 90

Significant advances are emerging in what concerns the newer inotropic agents. Despite the ideal agent, whose sole action is to increase the sensitivity of contractile proteins to calcium is yet to be found, the identification of specific receptors of dopamine in the CNS and peripheral circulation, had stimulated the pharmacological research of dopaminergic receptors agonists, selective for the subtypes DA1 and DA2, selective DA1 and DA2 antagonists and the dopamine beta-hidroxilase inhibitors and represent an unequivocal value. Beta-adrenergic agonists have been extensively evaluated as positive inotropic agents in the patients with congestive heart failure. Although norepinephrine, epinephrine and isoproterenol are potent stimulators of myocardial beta-adrenergic receptors, the clinical use of these agents has been limited by their positive chronotropic actions and their tendency to exacerbate cardiac arrhythmias (epinephrine and isoproterenol); their potent effects on vascular alpha 1-adrenergic receptors, which cause vasoconstriction (norepinephrine); and their effects on vascular beta 2 receptors, which cause vasodilation (isoproterenol). Dopamine, endogenous precursor of norepinephrine, is a sympathomimetic amine that has been widely used clinically as a cardiac stimulant. The effects of this drug are due to a combination of its actions on alpha, beta, and dopaminergic receptors, as well as a tyramine-like effect that causes the release of endogenous norepinephrine. Dopamine's positive inotropic effects are due principally to stimulation of cardiac beta-adrenergic receptors. At low doses it also stimulates renal dopaminergic receptors, thereby increasing renal cortical blood flow and promotion diuresis; higher doses causes stimulation of alpha 1-adrenergic receptors, resulting in increasing systemic arterial and venous pressures and, potentially, decrease renal blood flow. This vasoconstrictor action is frequently undesirable in patients with severe heart failure, and limits the drug's usefulness as a positive inotropic agent. Despite this risk, the use of synthetically derived catecholamines, i.e. dobutamine, has gained wide acceptance for the treatment of low output state associated with systemic hypotension. Despite the well reported down regulation of beta 1-adrenergic receptors in patients with chronic congestive heart failure, dobutamine consistently exerts hemodynamic benefits in this clinical situation. An attenuation of these benefits may be observed at times, although new tachyphylaxis very rarely occurs. Since dobutamine does not preferentially dilate the renal vasculature, concomitant administration of dopamine, at a dose which only stimulates the dopaminergic receptors in the renal artery, had the advantage of increasing renal perfusion and improving renal function. Administration of dopamine is often prolonged after that of dobutamine, and may help the wearing off of dobutamine.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[New inotropic agents in the treatment of congestive heart failure]. 790 58