CARDIAC FAILURE: Sympathetic stimulation may be essential for support of the circulation in individuals with diminished myocardial contractility, and its inhibition by β-adrenergic receptor blockade may precipitate more severe failure. Although β-blockers should be avoided in overt cardiac failure, acebutolol can be used with caution in patients with a history of heart failure who are controlled with digitalis and/or diuretics. Both digitalis and acebutolol impair AV conduction. If cardiac failure persists, therapy with acebutolol should be withdrawn.

IN PATIENTSWITHOUT A HISTORY OF CARDIAC FAILURE: In patients with aortic or mitral valve disease or compromised left ventricular function, continued depression of the myocardium with β-blocking agents over a period of time may lead to cardiac failure. At the first signs of failure, patients should be digitalized and/or be given a diuretic and the response observed closely. If cardiac failure continues despite adequate digitalization and/or diuretic, acebutolol therapy should be withdrawn.

EXACERBATION OF ISCHEMIC HEART DISEASE FOLLOWING ABRUPT WITHDRAWAL: Following abrupt cessation of therapy with certain β-blocking agents in patients with coronary artery disease, exacerbation of angina pectoris and, in some cases, myocardial infarction and death have been reported. Therefore, such patients should be cautioned against interruption of therapy without a physician’s advice. Even in the absence of overt ischemic heart disease, when discontinuation of acebutolol is planned, the patient should be carefully observed, and should be advised to limit physical activity to a minimum while acebutolol is gradually withdrawn over a period of about two weeks. (If therapy with an alternative β-blocker is desired, the patient may be transferred directly to comparable doses of another agent without interruption of β-blocking therapy.) If an exacerbation of angina pectoris occurs, antianginal therapy should be restarted immediately in full doses and the patient hospitalized until his condition stabilizes.

PERIPHERAL VASCULAR DISEASE: Treatment with β-antagonists reduces cardiac output and can precipitate or aggravate the symptoms of arterial insufficiency in patients with peripheral or mesenteric vascular disease. Caution should be exercised with such patients, and they should be observed closely for evidence of progression of arterial obstruction.

BRONCHOSPASTIC DISEASES: PATIENTS WITH BRONCHOSPASTIC DISEASE SHOULD, IN GENERAL, NOT RECEIVE A β-BLOCKER. Because of its relative β1-selectivity, however, low doses of acebutolol may be used with caution in patients with bronchospastic disease who do not respond to, or who cannot tolerate, alternative treatment. Since β1-selectivity is not absolute and is dose-dependent, the lowest possible dose of acebutolol should be used initially, preferably in divided doses to avoid the higher plasma levels associated with the longer dose-interval. A bronchodilator, such as theophylline or a β2-stimulant, should be made available in advance with instructions concerning its use.

ANESTHESIA AND MAJOR SURGERY: The necessity, or desirability, of withdrawal of a β-blocking therapy prior to major surgery is controversial. β-adrenergic receptor blockade impairs the ability of the heart to respond to β-adrenergically mediated reflex stimuli. While this might be of benefit in preventing arrhythmic response, the risk of excessive myocardial depression during general anesthesia may be enhanced and difficulty in restarting and maintaining the heart beat has been reported with beta-blockers. If treatment is continued, particular care should be taken when using anesthetic agents which depress the myocardium, such as ether, cyclopropane, and trichlorethylene, and it is prudent to use the lowest possible dose of acebutolol.

Acebutolol, like other β-blockers, is a competitive inhibitor of β-receptor agonists, and its effect on the hear t can be reversed by cautious administration of such agents (e.g., dobutamine or isoproterenol – see Overdosage).

Manifestations of excessive vagal tone (e.g., profound bradycardia, hypotension) may be corrected with atropine 1 to 3 mg IV in divided doses.

DIABETES AND HYPOGLYCEMIA: β-blockers may potentiate insulin-induced hypoglycemia and mask some of its manifestations such as tachycardia; however, dizziness and sweating are usually not significantly affected. Diabetic patients should be warned of the possibility of masked hypoglycemia.

THYROTOXICOSIS: β-adrenergic blockade may mask certain clinical signs (tachycardia) of hyperthyroidism. Abrupt withdrawal of β-blockade may precipitate a thyroid storm; therefore, patients suspected of developing thyrotoxicosis from whom acebutolol therapy is to be withdrawn should be monitored closely.