atenolol
(a ten' o lole)
Apo-Atenolol (CAN), Gen-Atenolol (CAN), Novo-Atenol (CAN), Tenolin (CAN), Tenormin

Pregnancy Category D

Drug classes
Beta1-selective adrenergic blocking agent
Antianginal drug
Antihypertensive drug

Therapeutic actions
Blocks beta-adrenergic receptors of the sympathetic nervous system in the heart and juxtaglomerular apparatus (kidney), thus decreasing the excitability of the heart, decreasing cardiac output and oxygen consumption, decreasing the release of renin from the kidney, and lowering blood pressure.

Indications
· Treatment of angina pectoris due to coronary atherosclerosis
· Hypertension, as a step 1 agent, alone or with other drugs, especially diuretics
· Treatment of myocardial infarction
· Unlabeled uses: prevention of migraine headaches; alcohol withdrawal syndrome, treatment of ventricular and supraventricular arrhythmias

Contraindications and cautions
· Contraindicated with sinus bradycardia, second- or third-degree heart block, cardiogenic shock, CHF.
· Use cautiously with renal failure, diabetes or thyrotoxicosis (atenolol can mask the usual cardiac signs of hypoglycemia and thyrotoxicosis), lactation.

Available forms
Tablets--25, 50, 100 mg; injection--5 mg/10 mL

Dosages
ADULTS
· Hypertension: Initially 50 mg PO once a day; after 1–2 wk, dose may be increased to 100 mg/day
· Angina pectoris: Initially 50 mg PO daily. If optimal response is not achieved in 1 wk, increase to 100 mg daily; up to 200 mg/day may be needed.
· Acute MI: Initially 5 mg IV given over 5 min as soon as possible after diagnosis; follow with IV injection of 5 mg 10 min later. Switch to 50 mg PO 10 min after the last IV dose; follow with 50 mg PO 12 hr later. Thereafter, administer 100 mg PO daily or 50 mg PO bid for 6–9 days or until discharge from the hospital.
GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT
Dosage reduction is required because atenolol is excreted through the kidneys. The following dosage is suggested:

Creatinine Clearance
mL/min
Half-life (hr)
Maximum Dosage
15–35
16–27
50 mg/day
< 15
> 27
25 mg/day


Patients on hemodialysis: 50 mg after each dialysis; give only in hospital setting; severe hypotension can occur.
Pediatric patients: Safety and efficacy not established.

Pharmacokinetics
Route
Onset
Peak
Duration
Oral
Varies
2–4 hr
24 hr
IV
Immediate
5 min
24 hr


Metabolism: T1/2: 6–7 hr
Distribution: Crosses placenta; passes into breast milk
Excretion: Urine (40%–50%) and bile/feces (50%–60%)

IV facts
Preparation: May be diluted in dextrose injection, sodium chloride injection, or sodium chloride and dextrose injection. Stable for 48 hr after mixing.
Infusion: Initiate treatment as soon as possible after admission to the hospital; inject 5 mg over 5 min; follow with another 5-mg IV injection 10 min later.

Adverse effects
· Allergic reactions: Pharyngitis, erythematous rash, fever, sore throat, laryngospasm, respiratory distress
· CNS: Dizziness, vertigo, tinnitus, fatigue, emotional depression, paresthesias, sleep disturbances, hallucinations, disorientation, memory loss, slurred speech
· CV: Bradycardia, CHF, cardiac arrhythmias, sinoatrial or AV nodal block, tachycardia, peripheral vascular insufficiency, claudication, CVA, pulmonary edema, hypotension
· Dermatologic: Rash, pruritus, sweating, dry skin
· EENT: Eye irritation, dry eyes, conjunctivitis, blurred vision
· GI: Gastric pain, flatulence, constipation, diarrhea, nausea, vomiting, anorexia, ischemic colitis, renal and mesenteric arterial thrombosis, retroperitoneal fibrosis, hepatomegaly, acute pancreatitis
· GU: Impotence, decreased libido, Peyronie's disease, dysuria, nocturia, frequent urination
· Musculoskeletal: Joint pain, arthralgia, muscle cramp
· Respiratory: Bronchospasm, dyspnea, cough, bronchial obstruction, nasal stuffiness, rhinitis, pharyngitis (less likely than with propranolol)
· Other: Decreased exercise tolerance, development of antinuclear antibodies, hyperglycemia or hypoglycemia, elevated serum transaminase, alkaline phosphatase, and LDH

Interactions
Drug-drug
· Increased effects with verapamil, anticholinergics, quinidine
· Increased risk of orthostatic hypotension with prazosin
· Increased risk of lidocaine toxicity with atenolol
· Possible increased blood pressure-lowering effects with aspirin, bismuth subsalicylate, magnesium salicylate, sulfinpyrazone, oral contraceptives
· Decreased antihypertensive effects with NSAIDs, clonidine
· Decreased antihypertensive and antianginal effects of atenolol with ampicillin, calcium salts
· Possible increased hypoglycemic effect of insulin
Drug-lab test
· Possible false results with glucose or insulin tolerance tests
Nursing considerations
Assessment
· History: Sinus bradycardia, second- or third-degree heart block, cardiogenic shock, CHF, renal failure, diabetes or thyrotoxicosis, lactation
· Physical: Baseline weight, skin condition, neurologic status, P, BP, ECG, respiratory status, kidney and thyroid function, blood and urine glucose

Interventions
· Do not discontinue drug abruptly after long-term therapy (hypersensitivity to catecholamines may have developed, causing exacerbation of angina, MI, and ventricular arrhythmias). Taper drug gradually over 2 wk with monitoring.
· Consult physician about withdrawing drug if patient is to undergo surgery (withdrawal is controversial).

Teaching points
· Take drug with meals if GI upset occurs.
· Do not stop taking this drug unless told to by a health care provider.
· Avoid driving or dangerous activities if dizziness, weakness occur.
· These side effects may occur: dizziness, light-headedness, loss of appetite, nightmares, depression, sexual impotence.
· Report difficulty breathing, night cough, swelling of extremities, slow pulse, confusion, depression, rash, fever, sore throat.

Adverse effects in Italic are most common; those in Bold are life-threatening.