Therabloc Warnings

Cardiac Failure: Sympathetic stimulation is necessary in supporting circulatory function in congestive heart failure, and β-blockade carries the potential hazard of depressing myocardial contractility and precipitating more severe failure. In patients who have congestive heart failure controlled by digitalis and/or diuretics, atenolol should be cautiously administered, since both digitalis and atenolol slow AV conduction.
However, latest clinical trials using other β-blockers, metoprolol, bisoprolol and carvedilol have been shown to improve symptoms and to decrease long-term cardiac morbidity and mortality among patients with chronic stable heart failure. However, initial doses used are small and titration to full dose is achieved after several weeks.
Patients with a History of Cardiac Failure: Continued depression of the myocardium with β-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 fully digitalized and/or be given a diuretic and the response observed closely. If cardiac failure continues despite adequate digitalization and diuresis, atenolol should be withdrawn.
Cessation of Therapy with Atenolol: Patients with coronary artery disease, who are being treated with atenolol, should be advised against abrupt discontinuation of therapy. Severe exacerbation of angina and the occurrence of myocardial infarction and ventricular arrhythmias have been reported in angina patients following abrupt discontinuation of therapy with β-blockers. As with other β-blockers, when abrupt discontinuation of atenolol is planned, the patients should be carefully observed and advised to limit physical activity to a minimum. If the angina worsens or acute coronary insufficiency develops, it is recommended that atenolol be promptly reinstituted, at least temporarily. Because coronary artery disease is common and may be unrecognized, it may be prudent not to discontinue atenolol therapy abruptly even in patients treated only for hypertension.
Use in pregnancy: Atenolol can cause fetal harm when administered to a pregnant woman. Atenolol crosses the placental barrier. Administration of atenolol, starting in the 2nd trimester of pregnancy, has been associated with birth of infants who are small for gestational age. Atenolol has been shown to cause a dose-related increase in embryonal and fetal resorptions in rats when given at dosages at ≥25 times the maximum human dosage, similar effects were not observed in rabbits receiving atenolol dosages up to 12.5 times the maximum human dosage. If the drug is used during pregnancy or if the patient becomes pregnant while taking atenolol, the patient should be appraised of the potential hazard to the fetus.