Metoprolol 0-antagonist

The use of selective P-antagonists for treatment of CHF has included the P -blocker metoprolol (Table 1) and results of clinical trials suggest long-term beneficial effects. Selective P -antagonists have also been tested, an example of which is xamoterol [81801 -12-9], C2 H25N20, which is (i)-A/-(2-hydroxy-3-(4-hydroxyphenoxy)propylamino)ethylmorphine-4-carboxamide. Xamoterol exhibits approximately 50% of the activity of isoproterenol, and serves to provide modest inotropic effects (128,129). 

Clinically used p-adrenergic receptor antagonists ( P-blockers ) are either px-selective (e.g. bisoprolol, metoprolol, atenolol, betaxolol) or non-selective,... 

Class II drugs are classical (3-adrenoceptor antagonists such as propranolol, atenolol, metoprolol or the short-acting substance esmolol. These drugs reduce sinus rate, exert negative inotropic effects and slow atrioventricular conduction. Automaticity, membrane responsiveness and effective refractory period of Purkinje fibres are also reduced. The typical extracardiac side effects are due to (3-adrenoceptor blockade in other organs and include bronchospasm, hypoglycemia, increase in peripheral vascular resistance, depressions, nausea and impotence. 

Class II antiarrhythmic drugs are (3-adrenoceptor antagonists such as propranolol, metoprolol or atenolol. (3-adrenoceptor antagonists slow sinus rate and atrioventricular conduction and exert negative inotropic effects. 

Controversy surrounds the selection of a P-blocker for HF management. First, although metoprolol and carvedilol are the most commonly used p-antagonists in HF, it remains controversial as to whether one agent should be considered first-line. Carvedilol exhibits several pharmacologic properties that theoretically would confer superior efficacy, since carvedilol (1) provides blockade at multiple adrenergic receptors, which... 

Similar to dihydropyridine calcium blockers, many 0-adrenoreceptor antagonists exhibit antioxidant activity. Mak and Weglinski [290] showed that the pretreatment of canine myocytic sarcolemmal membranes with 0-adrenoreceptor antagonists (propranolol, pindolol, metoprolol, atenolol, or sotalol) (Figure 29.15) inhibited superoxide-induced sarcolemmal... 

Fig. 4.5 Central receptor occupancy after oral administration of p-adrenoceptor antagonists A, atenolol B, metoprolol C, pindolol D, propranolol. The high occupancy of pi receptors does not correlate with physicochemical properties (lipophilicity). The occupation of p2 receptors correlates with sleep disturbances and the intrinsic selectivity of the compounds.

Metalol, 41 Metformin, 20 Methacycline, 227 Methadone, 328 Methionine enkephalin, 317 Methisazone, 350 Methixene, 413 17-Methyltestosterone, 156 Methgnodlol diacetate, 149 Methysergide, 477 Metiamide, 252 Metiapine, 429 Metizoline, 256 Metolazone, 384 Metoprolol, 109 Mexenone, 175 Mianserin, 451 Mibolerone, 144 Miconazole, 249 Midaflur, 259 Migraine, 477 Milipertine, 341 Mimbane, 347 Mineralocorticoids, 177 Minocycline, 228 Mixed agonists-antagonists, 318... 

A large number of (3-blockers are on the market in the United States. Of these, propranolol, a nonselective (3-antagonist, was the first to be introduced and is the prototypical drug with which the others are compared. Metoprolol was the hrst (3i-selective drug and timolol the hrst (3-blocker approved for ophthalmic use. 

D. Propranolol and metoprolol are selective for (3-receptors, whereas prazosin and phenoxybenzamine are selective for a-receptors. Labetalol is the only antagonist in this list that has the ability to reduce responses mediated by both a- and (3-receptors. 

A. Both sets of responses to isoproterenol are mediated by p-adrenoceptors, and all the choices are p-antagonists. However, drug X is more effective in antagonizing cardiac responses to isoproterenol than it is the bronchiolar responses. Drug X is therefore a cardioselective p-blocker, that is, selective for Pi over P2 receptors. Metoprolol is the only pi-selective antagonist among the choices. 

II Propranolol Metoprolol Nadolol Acebutolol Atenolol Pindolol Timolol Sotalol EsmoloF 3-Adrenoceptor antagonist, cardiac membrane stabilization, indirect effect on sinoatrial node to decrease rate of spontaneous diastolic depolarization. Indirect effect on A-V node to decrease conduction velocity and prolong ERR... 

P-Blockers approved for clinical use in secondary angina in the United States include propranolol and nadolol (Corgard), compounds that block both Pi- and Pj-adrenoceptors equally, while atenolol (Tenormin) and metoprolol (Lopressor) are cardioselective Pi-receptor antagonists. 

Beta-adrenoceptor antagonists are used to treat hypertension, angina pectoris, arrhythmias and secondary myocardial infarct prevention following primary infarction (timolol, metoprolol and propranolol). 

Propranolol reduces the frequency and intensity of migraine headache. Other 13-receptor antagonists with preventive efficacy include metoprolol and probably also atenolol, timolol, and nadolol. The mechanism is not known. Since sympathetic activity may enhance skeletal muscle tremor, it is not surprising that 13 antagonists have been found to reduce certain tremors (see Chapter 28). The somatic manifestations of anxiety may respond dramatically to low doses of propranolol, particularly when taken prophylactically. For example, benefit has been found in musicians with performance anxiety ("stage fright"). Propranolol may contribute to the symptomatic treatment of alcohol withdrawal in some patients. 

However, contrary to popular belief, beta-adrenoceptor antagonists do not by themselves increase the risk of hypoglycemic episodes in insulin-treated diabetics, in whom their use was concluded to be generally safe (192). Indeed, in 20 such patients treated with diet or diet plus oral hypoglycemic agents, both propranolol and metoprolol produced small but significant increases in blood... 

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