Propranolol in the treatment of angina: a review.

The use of beta-adrenergic blocking drugs in angina pectoris was one of the original indications for these drugs suggested by Black. An anti-anginal effect was demonstrated with the first beta-adrenergic blocking drug, pronethalol, that was used clinically. This benefit in angina was confirmed in the early trials with propranolol in 1964-65. Although some definite anti-anginal effect can be demonstrated with low fixed dosage, evidence suggested that those trials which used a higher and a variable dose displayed a greater anti-anginal action of the drug. After a two dose trial (Gillam and Prichard, 1966,) demonstrated a dose dependent anti-anginal effect, a log-dose response study demonstrated a progressive reduction in angina attacks as dosage was increased (Prichard and Gillam, 1971). While a highly significant effect was found with an average dose of 52 mg a day a progressive reduction in angina attacks was found with logarithmic increases in dosage up to an average of 417 mg a day. Dosage in this trial was adjusted to produce a supine heart rate of 55-60 beats/minute provided this was not prevented by side effects. As the dosage of 417 mg a day was still on the straight line part of the dose response curve and therefore suboptimal, we not adjust dosage to produce a standing heart rate of 55-60. Fully meaningful comparative trials require that optimum dose of the drugs being compared are used. A variable dose comparative trial comparing propranolol and practolol, showed propranolol was the more effective agent. More recently a variable dose comparative trial of sotalol and propranolol indicated propranolol had greater anti-anginal action although sotalol, unlike practolol, was more effective than low dose propranolol. The use of beta-blocking agents in angina pectoris is relatively safe provided that the contraindications of asthma and cardiac insufficiency are observed and that treatment is commenced at a low dosage. The most dramatic change in the sympathetic environment of the heart takes place when treatment with a beta-blocking drug is commenced. The greatest danger of precipitating heart failure is therefore at the beginning of treatment even with a small starting dose. Once treatment has begun even an increase of 25% per dose represents a small pharmacological increment as there is no great change in the sympathetic drive to the heart. The larger dosage of beta-blocking drugs required for optimum treatment of angina may be gradually approached, but it has been my experience that heart failure is not likely to be precipitated at larger doses, provided they are not used initially. In other than mild angina pectoris the average optimum dosage of propranolol is 500-800 mg a day, similar, or perhaps more than the average dose in hypertension.