02-Adrenoreceptors side effects

Salbutamol is a beta-adrenoreceptor agonist that is used in asthma or chronic obstructive pulmonary disease in order to exert bronchodilation. Side-effects... 

There has been considerable interest in the enantiomers of salmeterol (2). Salmeterol (2) is a long acting, potent (32 adrenoreceptor agonist. The (7 )-enantiomer is more potent than the (S)-enantiomer, however, it has been recently claimed that the (S)-enantiomer has a higher selectivity for P2 receptors and thus exhibited fewer side-effects than the (/ )-enantiomer or the racemate. ... 

Correct answer = A. A bidirectional block can decrease arrhythmias caused by reentry. All antiarrhythmic drugs exert some negative inotropic effect and decrease cardiac output. The i side effects of this group of drugs are serious and include arrhythmias that can lead to sudden death. Some antiarrhythmic drugs affect K+ or Ca++ channels, or p adrenoreceptors. 

Labetalol is a p-blocker with nonselective p- and selective Uj-adreno-receptor antagonist properties. With relatively high doses, labetalol elicits postural hypotension, an undesirable side-effect. Dilevalol is one of the four isomers (R, R) of labetalol that is almost devoid of a-adrenoreceptor activity. Hence, the reduction in peripheral vascular resistance observed for dilevalol occurs via its pj-agonist activity, which is not associated with postural hypotension. This renders dilevalol suitable for physically active hypertensive patients and those who complain of cold extremities (19). However, administration of dilevalol has been reported to be associated with a few reversible cases of hepatiris and jaundice (20). Hence, it is unlikely that this drug will become available as a new p-blocker. 

Mirtazapine (Remeron) is a new antidepressant with an entirely new mode of action. It is an alpha2-adrenoreceptor blocker, producing increased noradrenergic and serotonergic activity. Common side effects include sedation and nausea. 

Prazosin is a selective competitive ai-adrenoreceptor antagonist widely used not only as a pharmacological tool for ai-adrenoreceptor subtypes characterization but also as an effective agent in the management of hypertension. Its antihypertensive activity depends on a peripheral vasodilatation mediated by a postjunctional aj-adrenoreceptor blockade. Moreover, given its high O]-selectivity, prazosin lacks side effects such as... 

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. 

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. 

Effects on other receptors are known (e.g., antimuscarinic and antihistaminic), but these appear to elicit mostly side effects. The hypothesis that arises—and may replace the biogenic amine concept partially—is that it may be the chronic exposure of central (32-adrenoreceptors to these elevated biogenic amines (NE, 5-HT, and maybe DA also) that is the basis of the action. The most likely effect now seems to be decreased sensitivity of these receptors. By measuring c-AMP levels, studies using long-term drug administration indicate that central (3-receptors become less responsive postsynaptically and also that central 5-HT and (Xi receptors may become enhanced. 

Another example of marked B-adrenoreceptor potency enhancement by N-substltution is illustrated by fenoterol (60a). which is strikingly more potent than its N-tert-butyl counterpart, ter-butallne (6. Fenoterol is a clinically effective bronchodilator by either oral or aerosol administration however, some cardiac stimulation and tremors are noted (136, 137). Cat soleus muscle, bronchial and heart rate experiments indicate selective B2 adrenoreceptor potency for 60b (138). Another resorcinol, one of a series of xanthine derivatives, is reproterol (60c). Repro-terol is clinically effective in bronchial asthma it causes minimum CNS and cardiovascular side effects upon administration orally or by inhalation, and tachyphylaxis is not observed (139). 

Considering that, studies have been developed to establish the toxicological profile of p-synephrine. The acute administration of C. aurantium extract (2.5 % p-synephrine) and p-synephrine produced reduction in locomotor activity, gasping, exophthalmia, piloerection, and salivation, corroborating to the hypothesis that p-synephrine acts not only in p3-adrenoreceptors but also in other adrenergic receptors. However, all the effects were reversible and persisted for 3 h. The adrenergic stimulation alerts for the same possible side effects of p-synephrine and C. aurantium [78]. The subchronic toxicity of Citrus aurantium extract and p-synephrine were also determined and indicated a low subchronic toxicity in mice but a possible alteration in the oxidative metabolism [79]. 

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 =). 

The main product of the Hofmann elimination of atracurium is laudanosine, an alpha-adrenoreceptor blocking agent which causes hypotension. Moreover, laudanosine crosses the blood-brain barrier (in contrast to the parent compound) and may cause excitement and seizure activity which leads to an increase in anaesthetic requirement by 30%. Accumulation and corresponding problems with laudanosine arise only in infants and with prolonged application in ICUs. ° Laudanosine-caused hypotension is enhanced by histamine released from tissue stores as a side effect of atracurium. 

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