Sympathomimetics direct acting

Sympathomimetics (directly acting) Combining MAOis with agents such as epinephrine or norepinephrine is relatively safe since MAOis cause them to accumulate in the nerve terminal (thus, they do not directly act on postsynaptic receptors). 

COMT inhibitors may inhibit the normal metabolism of ephedrine (and the catecholamines it releases at adrenergic nerve endings), which could result in a marked exaggeration of its normal effects. See also COMT inhibitors -I- Sympathomimetics Directly-acting , above. 

Note that drugs with directly-acting sympathomimetic effects (of which beta agonists are an example) do not normally interact to cause hypertension with MAOIs, see sympathomimetics directly-acting , (below). However, phenylephrine (which has some indirect actions, see sympathomimetics phenylephrine , (p.l 148)) may have contributed to the reaction between toloxatone and terbutaline, and the fact that terbutaline seems to have been given orally would also have eontributed. The hypomania reaction is not understood. 

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. 

Terbutaline is a synthetic sympathomimetic amine. It is one of the most selective direct-acting stimulants of )32 dr6noreceptors. It stimulates smooth muscle )32-adrenoreceptors in the bronchi, relaxing them and relatively minutely acting on the — receptors of the heart. 

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. 

Bromocriptine (Parl el) [Antiparkinsonian Agent/Dopamine Receptor Agonist] Uses Parkin on Dz, hyperprolactinemia, acromegaly, pituitary tumors Action Direct-acting on the striatal dopamine receptors X prolactin secretion Dose Initial, 1.25 mg PO bid titrate to effect, w/ food Caution [B, ] Contra Severe ischemic heart Dz or PVD Disp Tabs, caps SE X BP, Raynaud phenomenon (vasospastic disorder resulting in discoloration of the fmgers/toes), dizziness, N, hallucinations Interactions T Effects W/ erythromycin, fluvoxamine, nefazodone, sympathomimetics, antihypertensives X effects W/ phenothiazines, antipsychotics EMS Monitor BP may cause intolerance to EtOH OD May cause NA, severe hypotension give IV fluids symptomatic and supportive... 

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. 

Mechanism of Action A sympathomimetic that directly acts on alpha-adrenergic receptors in arterioles of the nasal mucosa to produce vasoconstriction resulting in decreased blood flow. Therapeutic Effect Decreased nasal congestion. Pharmacokinetics Onset of acf ion occurs wif hin 5-10 minuf es for a duration of action of 5-6 hours. Well absorbed fhrough nasal mucosa. May also be systemically absorbed from bofh nasal mucosa and gasfroinfesfinal (GI) fracf. Half-life Unknown. 

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. 

Direct-acting agonists typically have a 3-hydroxyl group, although dopamine does not. In addition to facilitating activation of adrenoceptors, this hydroxyl group may be important for storage of sympathomimetic amines in neural vesicles. 

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... 

Sympathomimetics act directly on receptors at nerve endings (direct acting) or indirectly by stimulating the release of norepinephrine from the nerve terminals (indirect acting), Some act by both mechanisms (mixed), For the purposes of this section, mixed sympathomimetics will be considered as direct acting,... 

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). 

CENTRALLY ACTING ANTI HYPERTENSIVES SYMPATHOMIMETICS-DIRECT Risk of t BP when donidine is given with epinephrine or norepinephrine Additive effect donidine use associated with t circulating catecholamines Monitor BP at least weekly until stable... 

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... 

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