Current status of labetalol, the first alpha- and beta-blocking agent.

Labetalol is a unique antihypertensive agent which is a competitive peripheral antagonist at both alpha- and beta-adrenoceptor sites. Clinically, it possesses about one fourth of the beta-adrenoceptor blocking activity of propranolol and one half of the alpha-adrenoceptor blocking activity of phentolamine with a beta- to alpha-blocking ratio of approximately 7:1. Nowadays, the clinical profile of labetalol is clearly defined. Perorally, it has often been used in the treatment of mild, moderate and severe hypertension and intravenously in the management of hypertensive emergencies. It offers many advantages over beta-blockers with no prominent side-effects. Hemodynamically, labetalol reduces blood pressure, heart rate and, first of all, peripheral resistance with almost no change in resting cardiac output or stroke volume. Labetalol appears to be useful particularly in patients whose blood pressure is not adequately controlled by beta-blockers alone or combined with a diuretic, but sometimes at the expense of postural hypotensive side-effects. It has proved to be safe in patients with coronary artery disease or after acute myocardial infarction and in pregnant patients, but in phaechromocytoma further clinical experience is needed. In induced hypotension during anesthesia and surgery no invasive blood pressure measurements are needed. The most frequent adverse effects include fatigue, postural hypotension, headache and gastrointestinal complaints. On the whole, labetalol expands the armamentarium of the practising physician in the treatment of hypertension of different origin.