Practolol is a beta-adrenergic antagonist that has been used in the emergency treatment of cardiac arrhythmias. Practolol is a cardio-selective beta-blocking agent with an intrinsic sympathomimetic action, but devoid of local anaesthetic effect. It has been found effective in post infarction arrhythmias. In early infarction it reduces the area of necrosis as measured by surface ST segment mapping. Practolol has also been shown to be an effective drug in treating angina. Long-term treatment revealed advantageous effects of practolol on the incidence of anginal attacks and the number of nitroglycerin tablets consumed in daily life. There was also a noticeable improvement in the ECG. The results obtained in a double-blind trial, with placebo, proved the effectiveness of the drug. The treatment enabled the patients to lead appreciably more active lives. A marked increase in work performance, depending on the dose applied, was confirmed in exercise tolerance tests. No side-effects which would call for discontinuance of the treatment were seen during long-term administration with doses up to 800 mg daily. Like other beta-adrenergic antagonists, practolol competes with adrenergic neurotransmitters such as catecholamines for binding at sympathetic receptor sites. Practolol binds at beta(1)-adrenergic receptors in the heart and vascular smooth muscle, inhibiting the effects of the catecholamines epinephrine and norepinephrine and decreasing heart rate, cardiac output, and systolic and diastolic blood pressure. Practolol, discovered in 1966, was removed from the market due to severe side effects including conjunctival scarring, fibrosis, and metaplasia.