Atenolol - Warnings and Precautions

WARNINGS Cardiac Failure Sympathetic stimulation is necessary in supporting circulatory function in congestive heart failure, and beta blockade carries the potential hazard of further depressing myocardial contractility and precipitating more severe failure.

IN PATIENTS WITHOUT A HISTORY OF CARDIAC FAILURE, continued depression of the myocardium with beta-blocking agents over a period of time can, in some cases, lead to cardiac failure.

At the first sign or symptom of impending cardiac failure, patients should be treated appropriately according to currently recommended guidelines, and the response observed closely.

If cardiac failure continues despite adequate treatment, atenolol and chlorthalidone should be withdrawn. (See DOSAGE AND ADMINISTRATION .) Renal and Hepatic Disease and Electrolyte Disturbances Since atenolol is excreted via the kidneys, atenolol and chlorthalidone should be used with caution in patients with impaired renal function.

In patients with renal disease, thiazides may precipitate azotemia.

Since cumulative effects may develop in the presence of impaired renal function, if progressive renal impairment becomes evident, atenolol and chlorthalidone should be discontinued.

In patients with impaired hepatic function or progressive liver disease, minor alterations in fluid and electrolyte balance may precipitate hepatic coma.

Atenolol and chlorthalidone should be used with caution in these patients.

Ischemic Heart Disease Following abrupt cessation of therapy with certain beta-blocking agents in patients with coronary artery disease, exacerbations of angina pectoris and, in some cases, myocardial infarction have been reported.

Therefore, such patients should be cautioned against interruption of therapy without the physician's advice.

Even in the absence of overt angina pectoris, when discontinuation of atenolol and chlorthalidone is planned, the patient should be carefully observed and should be advised to limit physical activity to a minimum.

Atenolol and chlorthalidone should be reinstated if withdrawal symptoms occur.

Because coronary artery disease is common and may be unrecognized, it may be prudent not to discontinue atenolol and chlorthalidone therapy abruptly even in patients treated only for hypertension.

Concomitant Use of Calcium Channel Blockers Bradycardia and heart block can occur and the left ventricular end diastolic pressure can rise when beta-blockers are administered with verapamil or diltiazem.

Patients with pre-existing conduction abnormalities or left ventricular dysfunction are particularly susceptible. (See PRECAUTIONS .) Bronchospastic Diseases PATIENTS WITH BRONCHOSPASTIC DISEASE SHOULD, IN GENERAL, NOT RECEIVE BETA-BLOCKERS.

Because of its relative beta 1 -selectivity, however, atenolol and chlorthalidone may be used with caution in patients with bronchospastic disease who do not respond to or cannot tolerate, other antihypertensive treatment.

Since beta 1 -selectivity is not absolute, the lowest possible dose of atenolol and chlorthalidone should be used and a beta 2 -stimulating agent (bronchodilator) should be made available.

If dosage must be increased, dividing the dose should be considered in order to achieve lower peak blood levels.

Major Surgery Chronically administered beta-blocking therapy should not be routinely withdrawn prior to major surgery, however the impaired ability of the heart to respond to reflex adrenergic stimuli may augment the risks of general anesthesia and surgical procedures.

Metabolic and Endocrine Effects Beta-blockers may prevent early warning signs of hypoglycemia, such as tachycardia, and increase the risk for severe or prolonged hypoglycemia at any time during treatment, especially in patients with diabetes mellitus or children and patients who are fasting (i.e., surgery, not eating regularly, or are vomiting).

If severe hypoglycemia occurs, patients should be instructed to seek emergency treatment.

Insulin requirements in diabetic patients may be increased, decreased or unchanged; latent diabetes mellitus may become manifest during chlorthalidone administration.

Beta-adrenergic blockade may mask certain clinical signs (e.g., tachycardia) of hyperthyroidism.

Abrupt withdrawal of beta blockade might precipitate a thyroid storm; therefore, patients suspected of developing thyrotoxicosis from whom atenolol and chlorthalidone therapy is to be withdrawn should be monitored closely.

Because calcium excretion is decreased by thiazides, atenolol and chlorthalidone should be discontinued before carrying out tests for parathyroid function.