atenolol
Tenormin

Available forms
Available by prescription only
Injection: 5 mg/10 ml
Tablets: 25 mg, 50 mg, 100 mg

Indications and dosages
 Hypertension. Adults: Initially, 25 to 50 mg P.O. as a single daily dose. May increase dose to 100 mg daily after 7 to 14 days. Higher doses are unlikely to produce further benefit.
 Chronic stable angina pectoris. Adults: 50 mg P.O. once daily; may be increased to 100 mg daily after 7 days for optimal effect. Maximum daily dose is 200 mg daily.
 To reduce risk of CV mortality in patients with acute MI. Adults: 5 mg I.V. over 5 minutes, followed by another 5 mg I.V. 10 minutes later. Start oral therapy (50 mg) 10 minutes after the final dose in patients who tolerate the full I.V. dose. Then, 50 mg P.O. 12 hours later. Thereafter, 100 mg P.O. daily or 50 mg P.O. b.i.d. for 6 to 9 days or until discharged from the hospital.
 To slow rapid ventricular response to atrial tachyarrhythmias following acute MI without left ventricular dysfunction and AV block ◇. Adults: 2.5 to 5 mg I.V. over 2 minutes, p.r.n., to control rate; no more than 10 mg over a 10- to 15-minute period.
≡ Dosage adjustment. For patients with renal failure, adjust dosage if creatinine clearance is below 35 ml/minute. If patient has creatinine clearance of 15 to 35 ml/minute, give 50 mg daily. If patient has creatinine clearance below 15 ml/ minute, give 25 mg daily. If patient is undergoing hemodialysis, dosage is 25 to 50 mg after each treatment under close supervision.

Pharmacodynamics
Antihypertensive action: Atenolol may reduce blood pressure by adrenergic receptor blockade, thereby decreasing cardiac output by decreasing the sympathetic outflow from the CNS and by suppressing renin release. At low doses, atenolol, like metoprolol, selectively inhibits cardiac beta₁-receptors; it has little effect on beta₂-receptors in bronchial and vascular smooth muscle.
Antianginal action: Atenolol aids in treating chronic stable angina by decreasing myocardial contractility and heart rate (negative inotropic and chronotropic effect), thus reducing myocardial oxygen consumption.
Cardioprotective action: The mechanism whereby atenolol improves survival in patients with MI is unknown. However, it does reduce the frequency of PVCs, chest pain, and enzyme elevation.

Pharmacokinetics
Absorption: About 50% to 60% of an atenolol dose is absorbed.
Distribution: Distributed into most tissues and fluids except the brain and CSF; about 5% to 15% is protein-bound.
Metabolism: Metabolized minimally.
Excretion: About 40% to 50% of a given dose is excreted unchanged in urine; remainder is excreted as unchanged drug and metabolites in feces. In patients with normal renal function, plasma half-life is 6 to 7 hours; half-life increases as renal function decreases.

Contraindications and precautions
Contraindicated in patients with sinus bradycardia, greater than first-degree heart block, overt cardiac failure, or cardiogenic shock. Use cautiously in patients at risk for heart failure and in those with bronchospastic disease, diabetes, and hyperthyroidism.

Interactions
Drug-drug. Alpha-adrenergic drugs (such as those found in OTC cold remedies), indomethacin, NSAIDs: May antagonize antihypertensive effects of atenolol. Monitor patient for effect.
Antihypertensives: May potentiate antihypertensive effect of these drugs. Monitor blood pressure.
Insulin, oral hypoglycemics: Alters dosage requirements in stable diabetic patients. Monitor serum glucose level.

Adverse reactions
CNS: fatigue, lethargy, vertigo, drowsiness, dizziness, mental depression, fever.
CV: bradycardia, hypotension, heart failure, intermittent claudication, changes in exercise tolerance and ECG.
GI: nausea, diarrhea, dry mouth.
GU: renal impairment, dysuria, nocturia, oliguria, proteinuria.
Hematologic: agranulocytosis, nonthrombocytopenic or thrombocytopenic purpura, thrombocytopenia, anemia.
Hepatic: liver dysfunction.
Metabolic: hyperkalemia, hyperglycemia, hypoglycemia.
Musculoskeletal: leg pain.
Respiratory: dyspnea, bronchospasm.
Skin: rash.

Effects on lab test results
• May increase BUN, creatinine, potassium, uric acid, transaminase, alkaline phosphatase, bilirubin, and LDH levels. May increase or decrease glucose level.
• May decrease platelet and granulocyte counts and hemoglobin.

Overdose and treatment
Signs and symptoms of overdose include severe hypotension, bradycardia, heart failure, and bronchospasm.
 After acute ingestion, empty stomach by emesis or gastric lavage; follow with activated charcoal to reduce absorption. Thereafter, treat symptomatically and supportively.

Special considerations
• Patient should take oral single daily dose at same time each day.
• Drug may be taken without food.
• Monitor blood pressure, heart rate, and ECG during I.V. administration.
• Dose may need to be reduced in patients with renal insufficiency.
• I.V. atenolol affords a rapid onset of the protective effects of beta blockade against reinfarction.
• Patients who can’t tolerate I.V. atenolol after an MI may be candidates for oral atenolol therapy. Some evidence suggests that gastric absorption of atenolol may be delayed in the early phase of MI. This may result from the physiologic changes that accompany MI or from the effects of morphine, which is commonly administered to treat chest pain. However, oral therapy alone may still provide benefits.
• I.V. atenolol may be given undiluted or diluted no more than 1 mg/minute.
• Protect medication from heat, direct light, and moisture and store at room temperature.
• Caution against abrupt withdrawal of medication; it may precipitate MI and increased angina.
Pregnant patients
• Atenolol can cause fetal harm (intrauterine growth retardation).
Breast-feeding patients
• Safety hasn’t been established. Recommend an alternative feeding method during therapy.
Pediatric patients
• Safety and efficacy in children haven’t been established; use only if potential benefit outweighs risk.
Geriatric patients
• Geriatric patients may require lower maintenance doses of atenolol because of increased bioavailability or delayed metabolism; they also may have greater adverse effects.

Patient education
• Stress importance of not missing doses, but tell patient not to double a missed dose, especially if taking drug once daily.
• Advise patient to seek medical approval before taking OTC cold preparations.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use