Fenoldopam (marketed under the brand name Corlopam) is a drug and synthetic benzazepine derivative which acts as a selective D1 receptor partial agonist. Fenoldopam is a rapid-acting vasodilator. It is an agonist for D1-like dopamine receptors and binds with moderate affinity to α2-adrenoceptors. It has no significant affinity for D2-like receptors, α1 and β adrenoceptors, 5HT1 and 5HT2 receptors, or muscarinic receptors. Fenoldopam is a racemic mixture with the R-isomer responsible for the biological activity. The R-isomer has approximately 250-fold higher affinity for D1-like receptors than does the S-isomer. Fenoldopam Mesylate Injection, USP is indicated for the in-hospital, short-term (up to 48 hours) management of severe hypertension when rapid, but quickly reversible, emergency reduction of blood pressure is clinically indicated, including malignant hypertension with deteriorating end-organ function.

Midodrine is a prodrug, i.e., the therapeutic effect of orally administered midodrine is due to the major metabolite desglymidodrine formed by deglycination of midodrine. Desglymidodrine diffuses poorly across the blood-brain barrier, and is therefore not associated with effects on the central nervous system. Administration of midodrine results in a rise in standing, sitting, and supine systolic and diastolic blood pressure in patients with orthostatic hypotension of various etiologies. Standing systolic blood pressure is elevated by approximately 15 to 30 mmHg at 1 hour after a 10-mg dose of midodrine, with some effect persisting for 2 to 3 hours. Midodrine has no clinically significant effect on standing or supine pulse rates in patients with autonomic failure. Midodrine forms an active metabolite, desglymidodrine, that is an alpha1-agonist, and exerts its actions via activation of the alpha-adrenergic receptors of the arteriolar and venous vasculature, producing an increase in vascular tone and elevation of blood pressure. Desglymidodrine does not stimulate cardiac beta-adrenergic receptors. Midodrine is used for the treatment of symptomatic orthostatic hypotension (OH). Midodrine is marketed under the brand names Amatine, ProAmatine, Gutron.

Milrinone, a synthetic dimethylxanthine derivative structurally related to theophylline and caffeine, is used in the treatment of peripheral vascular diseases and in the management of cerebrovascular insufficiency, sickle cell disease, and diabetic neuropathy. Milrinone inhibits erythrocyte phosphodiesterase, resulting in an increase in erythrocyte cAMP activity. Subsequently, the erythrocyte membrane becomes more resistant to deformity. Along with erythrocyte activity, Milrinone also decreases blood viscosity by reducing plasma fibrinogen concentrations and increasing fibrinolytic activity. Milrinone is indicated for the treatment of congestive heart failure. Milrinone was marketed under the brand name Primacor.

Inamrinone (Amrinone) is a positive inotropic cardiotonic with vasodilator properties, phosphodiesterase inhibitory activity, and the ability to stimulate calcium ion influx into the cardiac cell. Inamrinone is a phosphodiesterase inhibitor (PDE3), resulting in increased cAMP and cGMP which leads to an increase in the calcium influx like that caused by beta-agonists resulting in increased inotropic effect. Inamrinone is used in the treatment of congestive heart failure.

Dobutamine is a sympathomimetic drug used in the treatment of heart failure and cardiogenic shock. Dobutamine hydrochloride is a direct-acting inotropic agent whose primary activity results from stimulation of the ß-receptors of the heart while producing comparatively mild chronotropic, hypertensive, arrhythmogenic, and vasodilative effects. It does not cause the release of endogenous norepinephrine, as does dopamine. Dobutamine directly stimulates beta-1 receptors of the heart to increase myocardial contractility and stroke volume, resulting in increased cardiac output. Dobutamine Injection, USP is indicated when parenteral therapy is necessary for inotropic support in the short-term treatment of adults with cardiac decompensation due to depressed contractility resulting either from organic heart disease or from cardiac surgical procedures.

Dopamine, a sympathomimetic amine vasopressor, is the naturally occurring immediate precursor of norepinephrine. G protein-coupled dopamine receptors (D1, D2, D3, D4, and D5) mediate all of the physiological functions of the catecholaminergic neurotransmitter dopamine, ranging from voluntary movement and reward to hormonal regulation and hypertension. Dopamine HCl is indicated for the correction of hemodynamic imbalances present in the shock syndrome due to myocardial infarction, trauma, endotoxic septicemia, open-heart surgery, renal failure, and chronic cardiac decompensation as in congestive failure.

Metaraminol is a potent sympathomimetic amine that increases both systolic and diastolic blood pressure, is an adrenergic receptor alpha-1 agonist.. Metaraminol is indicated for prevention and treatment of the acute hypotensive state occurring with spinal anesthesia. It is also indicated as adjunctive treatment of hypotension due to hemorrhage, reactions to medications, surgical complications, and shock associated with brain damage due to trauma or tumor. Metaraminol is also used in the treatment of priapism, in spite of this application was not approved, it appears to be effective.

Droxidopa (Northera, Chelsea Therapeutics) is a synthetic catecholamino acid precursor of norepinephrine indicated for the treatment of orthostatic dizziness or lightheadedness in adult patients with symptomatic neurogenic orthostatic hypotension (NOH) caused by primary autonomic failure, dopamine beta-hydroxylase deficiency, and non-diabetic autonomic neuropathy. Droxidopa was approved as oral therapy in February 2014 under the FDA’s accelerated approval program. Droxidopa is directly metabolized to norepinephrine by dopadecarboxylase. The specific mechanism of action of the drug is not known completely, but it is supposed to exert the pharmacological effects through norepinephrine and not through the parent molecule or other metabolites. It increases blood flow to the brain by stimulating peripheral arterial and venous vasoconstriction.

Ephedrine (l-form) is an alkaloid, which was initially purified from Ephedra plant. The extract form Ephedra has been used in China for medicinal purposes for several thousand years. Ephedrine acts as an agonist at alpha- and beta-adrenergic receptors and indirectly causes the release of norepinephrine from sympathetic neurons. The drug crosses the blood brain barrier and stimulates the central nervous system. Ephedrine products are now banned in many countries, as they are a major source for the production of the addictive compound methamphetamine. FDA has approved ephedrine only for the treatment of clinically important hypotension occurring in the setting of anesthesia.

Arbutamine was indicated to elicit acute cardiovascular responses in order to aid in diagnosing the presence or absence of coronary artery disease in patients who cannot exercise adequately. Arbutamine is a synthetic catecholamine with positive chronotropic and inotropic properties. The chronotropic (increase in heart rate [HR]) and inotropic (increase in force of contraction) effects of arbutamine serve to mimic exercise by increasing cardiac work (producing stress) and provoke myocardial ischemia in patients with compromised coronary arteries. In functional assays, arbutamine is more selective for beta-adrenergic receptors than for alpha-adrenergic receptors. The beta-agonist activity of arbutamine provides cardiac stress by increasing HR, cardiac contractility, and systolic blood pressure.