Cardiac failure beta, agonists

The drugs that were developed some 40 years ago as general beta-adrenoceptor agonists have largely fallen into disuse with the development of more selective betai-adrenoceptor agonists (for use in cardiac failure) and beta2-adrenoceptor agonists (for use in airways disease and threatened premature labor). 

Xamoterol is a beta-adrenoceptor antagonist/partial agonist that was developed for use in mild cases of cardiac failure and to treat atrial fibrillation (1). In more severe cases, however, it can actually worsen heart failure and increase mortality (2), because when sympathetic nervous system activity is high its beta-adrenoceptor antagonist properties predominate. It has therefore been withdrawn from the market (SEDA-18,159). 

Drugs used to combat heart failure include those that decrease preload (e.g diuretics, ACE inhibitors, AT-1 receptor antagonists, and vasodilators), those that decrease afterload (e.g., ACE inhibitors, AT-1 receptor antagonists, and vasodilators), and those that increase cardiac contractibility (e.g., digitalis, beta agonists, and bipyridines). 

Beta agonists increase cardiac rate and force and increase myocardial oxygen demand they are generally contraindicated in angina. In chronic heart failure, the heart is already subject to excessive sympathetic drive. The absence of Pj receptors in the cutaneous vascular bed makes beta agonists useless in conditions involving reduced skin blood flow. Uterine and bronchiolar smooth muscle are relaxed by beta, agonists. The answer is (B). 

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