The pharmacology of xamoterol: a basis for modulation of the autonomic control of the heart.

1. Xamoterol (Corwin, Carwin, Corwil, Xamtol, ICI 118,587) is a beta-adrenoceptor partial agonist which is of benefit in the chronic treatment of heart failure (e.g. The German and Austrian Xamoterol Study Group, 1988). These results contrast with those obtained with other beta-adrenoceptor drugs, prenalterol and pirbuterol which were unsuccessful on chronic dosing (Currie et al., 1984; Glover et al., 1985). 2. Unlike prenalterol and pirbuterol, xamoterol has no significant agonist activity at the beta 2-adrenoceptor and has shown no tachyphylaxis in animals or man. 3. The overall action of xamoterol is to modulate sympathetic control of the heart such that at rest and at low levels of exercise the heart receives inotropic support whilst during more severe exercise, heart rate is reduced. In patients with left ventricular dysfunction these effects lead to an improvement in the relation between filling pressure and cardiac output at all levels of activity such that a given cardiac output is achieved with a lower filling pressure. It is suggested that this alteration in the pattern of cardiac activity over a long period of time results in a beneficial adaptation of the myocardium and is a possible explanation of the observed clinical improvement.