0-Adrenoreceptor stimulant

Ritodrine is a selective Sj-adrenoreceptor stimulant, predominantly of the urino-genital system. It is used as a tocolytic agent for problems associated with premature miscarriages, and only in specialized medical facilities. Synonyms of ritodrine are yutopar and pre-par. 

Clinical studies showed that elderly patients are more sensitive to drugs such as sedatives, hypnotics, and analgesics. The most extensive studies show a decrease in responsiveness to /3-adrenoreceptors, stimulants, and blockers. Hypothermia is poorly tolerated by the elderly, as their body temperature regulation is impaired. 

Hall, I.P. and Hill, S.J. (1988). -Adrenoreceptor stimulation inhibits histamine-stimulated inositol phospholipid hydrolysis in bovine tracheal smooth muscle. Br. J. Pharmacol. 95, 1204-1212. 

Psychotomimetic drugs biochemistry and pharmacology. 7. 165 Purine receptors and their pharmacological roles, 18. 292 The Rate of contemporary drug discovery. 8. I Recent /3-adrenoreceptor stimulants. 5. 197... 

Beta2 adrenoreceptor stimulants cause bronchodilation by acting on adrenoreceptors in bronchial smooth muscle. Although they are selective for 2 receptors these drugs do have some affect on cardiac Pi receptors. Cardiac side effects are not usually a problem at therapeutic doses, but could be if a patient decided to increase the dose above that recommended. 

P2 adrenoreceptor stimulants are used as first choice for the rapid relief of an acute asthmatic attack and maintenance treatment of chronic asthma. They are more effective in treatment of the immediate phase reaction than the late phase reaction. P2 adrenoreceptor stimulants are less effective in chronic bronchitis, possibly because in this disease bronchoconstriction is due to reflex stimulation of acetylcholine receptors following stimulation of local irritant receptors in lung tissue. 

Side effects of P2 adrenoreceptor stimulants are rare but include ttemor, nervous tension, headache, peripheral vasodilation, tachycardia (increased heart rate), and hypokalae-mia (low potassium levels) after high doses, and hypersensitivity reactions. 

Antimuscarinic drugs are used to relieve, or at least partially reverse, bronchoconstriction that is refractory to P2 adrenoreceptor stimulants. These drugs work by blocking acetylcholine receptors (the so-called muscarinic receptors) in the bronchioles. This effectively prevents bronchoconstriction in response to parasympathetic stimulation. They may be used in combination with other bronchodilators. Antimuscarinics are of particular use in chronic bronchitis where the airways seem resistant to P2 receptor stimulation and because they also reduce mucus secretion. They are most frequently used as aerosol inhalers and in nebulizers. 

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. 

The sulfamlde has B-adrenoreceptor stimulant potency intermediate between the ethyl (18) and isopropyl (19) carbani-lates. ... 

PROBLEM 16.67 Metaproterenol (orciprenaline, 1) is a P-adrenoreceptor stimulant used therapeutically as a bron-chodilator. In the synthesis of the hydrobromide salt of racemic 1, outlined below, supply the appropriate reagents. 

BS 110—141, N-amidino-2-(2,6-dichlo-rophenyljacetamide HCl is a guanidine derivative, but its pharmacological action resembles that of clonidine it possesses a central os-adrenoreceptor stimulant activity and causes a centrally induced fall in blood pressure, due probably to lowering of sympathetic activity and reduction of circulatory pressor reflexes. Apparently because of this, postural hypotension seems to be rare. In a series of 15 patients some general side effects were recorded and (surprisingly) the development of a tremor in 5 on a 3—6 mg daily dose (22 =). 

Plm - plasmalemma, CW -cell wall, ChE- cholinesterase, ChR - cholinoreceptor, AdR -adrenoreceptor, Glc-glucosidase, I - Inhibition, S-stimulation,l50 or S50 - concentration, which inhibits or stimulate the process by 50 %, N - no effect, (-) - no experiments... 

Together with the CNS, compounds of this group affect the nervous system. They indirectly stimulate a- and fi- adrenoreceptors. The adrenomimetic properties of these compounds are similar to the properties of norepinephrine (noradrenaline) however, they are quite inferior to them in terms of activity. 

Norepinephrine is the primary neurotransmitter produced and released by adrenergic neurons, and in literature it is also described as and called (-) noradrenaline or levarterenol. This vasopressor catecholamine reduces both the resistance and capacity of blood vessels by stimulating a-adrenoreceptors and having a direct cardiostimulatory effect, which is accomplished by activation of )3i-adrenoreceptors. Norepinephrine exhibits significantly less activity than epinephrine as a drug for widening blood vessels through the activation of jSj-adrenoreceptors. Elevation of both stylistic and diastolic blood pressure is a typical reaction to intravenous introduction of norepinephrine. 

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. 

Clonidine is a selective o -adrenergic agonist. Clonidine has expressed hypotensive action, which is associated with a reduction of general peripheral vascular resistance, reduced frequency of cardiac beats, and a reduction of cardiac output. The mechanism of action of clonidine is caused by stimulation of o -adrenoreceptors of the inhibitory structures of the brain as well as a reduction of sympathetic impulses to the blood vessels and brain. 

Dopamine is found in every sympathetic neuron and ganglion in the CNS. As a drug, and in addition to stimulation of dopaminergic receptors, dopamine indirectly stimulates both a- and )3-adrenoreceptors. Dopamine also causes a release of endogenous norepinephrine. The mechanism of action is based on the excitatory effect on )3-adrenoreceptors (in low and moderate doses), as well as on a-adrenoreceptors (in large doses). It has a positive inotropic effect on the heart, increases blood supply, selectively widens renal and mesenteric blood vessels, does not elevate blood pressure, and slightly increases the frequency of heartbeats. 

Ephedrine is an alkaloid that is present in various forms of the ephedrine family, and which is still extracted from Ephedra sinica and Ephedra equisetina. Because of the presence of two asymmetric atoms, there are four isomeric forms. Pseudoepinephrine (d-isoephrine) is a stereoisomer with pharmacological action that differs slightly from ephedrine. The pharmacological action of ephedrine is typical of noncatecholamine sympathomimetics of mixed action. It stimulates both a- and 8-adrenoreceptors, and simultaneously causes a release of norepinephrine from synaptic neurons. Its vasoconstrictive ability is approximately 100 times weaker than that of epinephrine however, the duration of action is approximately 10 times longer. It is much less toxic than epinephrine, which allows it to be used widely in medicine. 

The mechanism of action of these drugs is caused by stimulation of o -adrenoreceptors in the inhibitory structure of the brain. It is believed that interaction of these drugs with adrenergic receptors is expressed in the suppression of vasomotor center neurons of the medulla, and reduction of hypothalamus activity, which leads to a decline in sympathetic impulses to the vessels and the heart. In summary, cardiac output and heart rate are moderately reduced, and consequently arterial pressure is reduced. 

Fenoterol is a selective stimulant of J -adrenoreceptors. It dilates bronchi and blood vessels, has a pronounced tocolytic action, lowers contractile activity and reduces uterus tonicity. It is mainly used in premature births. Synonyms of this drag are berodual, verotec, duovent, and others. 

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