Direct-acting sympathomimetic

Increased pharmacologic effects of direct-acting sympathomimetics decreased effects of indirect-acting sympathomimetics Increased therapeutic and possibly toxic effects of both drugs CNS stimulation tachycardia... 

Isoetharine is a direct-acting sympathomimetic with relatively low selectivity with j32-adrenoreceptors. However, it quickly calms bronchospasms better than more selective bronchodilators. It is used in treating chronic obstructive illnesses of outer respiratory tract. Synonyms of this drug are asthmalitan and bronkosol. 

Pharmacology Epinephrine, a direct-acting sympathomimetic agent, acts on and receptors. Topical application, therefore, causes conjunctival decongestion (vasoconstriction), transient mydriasis (pupillary dilation), and reduction in intraocular pressure (lOP). It is believed lOP reduction primarily is caused by reduced aqueous production and increased aqueous outflow. The duration of decrease in lOP is 12 to 24 hours. 

Mechanism of Action A direct-acting sympathomimetic amine that acts on alpha-adrenergic receptors in arterioles of the nasal mucosa to produce constriction. Therapeutic Effect Causes vasoconstriction resulting in decreased blood flow and decreased nasal congestion. 

It is a directly acting sympathomimetic amine used in symptomatic relief in nasal congestion which increases mucosal secretion. 

Tricyclic antidepressants potentiate the pressor effects of directly acting sympathomimetic amines, such as adrenaline (epinephrine) or noradrenaline (norepinephrine), to cause hypertension. Small amounts of these, such as may be present in local anaesthetic solutions, can be dangerous. Tricyclic antidepressants will inhibit the antihypertensive effects of the older anti hypertensive drugs, such as adrenergic neurone-blocking agents, e.g. guanethidine, a-methyl-DOPA, and clonidine. 

Tricyclic antidepressants + directly acting sympathomimetic amines (e.g. noradrenaline, adrenaline) —> hypertension and arrhythmias due to enhancement of the sympathomimetic effects. 

Sympathomimetics Increased pharmacologic effects of direct-acting sympathomimetics decreased... 

Directly acting sympathomimetics include epinephrine and dipivefrine (alpha and beta respectively) phenylephrine, metaraminol, norepinephrine, brimonidine and apraclonidine (alpha) dopamine and dobutamine (beta-1) and dopexamine and isoprenaline (cardiac beta-2). 

THEOPHYLLINE DIRECTLY ACTING SYMPATHOMIMETICS Case report of marked tachycardia when dobutamine was given to a patient already taking theophylline Uncertain Carefully titrate the dose of dobutamine in patients taking theophylline therapy... 

Direct-acting Sympathomimetics Directly stimulate receptors... 

Postjunctional receptors can be activated by many direct-acting sympathomimetics. These receptors are also targets for many antagonist drugs. 

Table 9-1. Direct-Acting Sympathomimetic Amines with -Activity0...

It is a directly acting sympathomimetic drug which is mostly used as a local vasoconstrictor for the relief of nasal congestion due to allergic or infectious manifestations. It is also employed as an ophthalmic solution for the relief of ocular congestion and blepharospasm. 

The drug exhibits a direct-acting sympathomimetic agent having predominantly P-adrenergic activity plus a selective action on the P2-receptors (i.e., (P2-agonist). This is, therefore, recommended for the treatment of severe and acute forms of bronchospasm via IM, IV, sub-cutaneous routes. 

It is closely related structurally to salbutamol, the only difference being that the former has a basic-pyridine nucleus while the latter has a benzene ring (nucleus). It is also a direct-acting sympathomimetic agent having a most prominent P-adrenoreceptor stimulant action, and a selective aetion on P2-receptors. 

Direct-acting sympathomimetics—directly stimulate receptors. 

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