Atenolol (Tenormin): Drug Whys
Generic name: Atenolol (multiple manufacturers)
Common U.S. brand names: Tenormin (AstraZeneca Pharmaceuticals, USA)
Popularity: Fourth most commonly prescribed drug between 2002-2006 (U.S.)
Class: Beta-Adrenergic blocker
Treatment Uses — For treatment of hypertension, usually in combination with other agents such as thiazide-type diuretics, angiotensin converting enzyme inhibitors (ACEI), angiotensin II receptor blockers (ARB) or calcium channel blockers (CCB). For treatment of angina, arrhythmias, to lengthen survival following myocardial infarction and in the treatment of heart failure. Used as prophylaxis before, during and after surgical procedures to reduce incidence of adverse cardiovascular events. May have benefit in treating migraine headaches, anxiety, alcohol withdrawal and pre-eclampsia. Used by performers to reduce symptoms of stage fright.
Dosing and Administration — In adults, the recommended oral starting dose is 50 milligrams once daily, adjusted upwards if necessary at weekly intervals to 100 milligrams daily. Pediatric use is not approved, but studies using atenolol for arrhythmias in children initially dose at 0.3 to 1.4 milligrams per kilogram given orally once daily and increase the daily dose every three to four days by 0.5 milligram per kilogram to a maximum of 2 milligrams per kilogram once daily. Similar oral doses have been suggested for pediatric hypertension, sometimes divided into two daily doses, titrated upwards not to exceed 2 milligrams per kilogram per day and a maximum of 100 milligrams total per day. An oral suspension of (2 milligrams per milliliter) atenolol can be prepared by a compounding pharmacy.
Intravenous atenolol is available but not widely used in the United States. Where used, it is typically reserved for adults requiring rapid beta blockade in the setting of acute or suspected myocardial infarction. Initial dosing is 5 milligrams intravenously over five minutes followed by a second 5 milligram dose given 10 minutes later. Patients who tolerate the full 10 milligram load are rapidly switched to oral dosing.
Absorption is affected by food, and atenolol should not be taken with meals although the actual clinical significance of this effect is questionable. Dose reductions are recommended for patients with renal (kidney) failure due to prolonged elimination. The amount of dose reduction depends largely on the degree of renal impairment. No adjustments appear necessary in patients with hepatic (liver) insufficiency or in the geriatric population.
Overdoses of atenolol generally manifest with lethargy and symptoms of excessive beta blockade such as wheezing, bradycardia and hypotension. Fluids are often ineffective and contraindicated due to heart failure caused by beta blockade. Intravenous glucagon is the drug of choice for its ability to improve heart rate and pump function independently of beta receptors. Doses up to 10 milligrams may be needed, followed by a continuous infusion until sufficient drug is eliminated or removed from the body. For IV doses above 2 mg, discard the (cadiotoxic) phenol diluent supplied and dilute with sterile water instead. Catecholamine infusions and pressors may be helpful, particularly when glucagon is ineffective, but will often require five to 15 times normal dosing to overcome beta receptor blockade. Hemodialysis is effective in removing atenolol from the body.
Pharmacology/Pharmacokinetics/Stability — Oral atenolol is rapidly absorbed. Peak blood levels are reached within two to four hours and a single dose exhibits beta blocking activity for up to 24 hours in healthy adults and up to 100 hours in patients with renal failure. Initial blood pressure lowering response is seen within three hours; peak blood pressure response takes from three to 14 days. Atenolol is not metabolized in the liver; 40 to 50 percent of an oral dose and 85 to 100 percent of an IV dose is excreted unchanged in the urine. Virtually all remaining atenolol is excreted unchanged in the feces. Use of atenolol during pregnancy can harm a fetus. Atenolol is excreted in breast milk; between 5.7 and 19.2 percent of an adult dose can be found in breast milk. The American Academy of Pediatrics rates atenolol as a drug that should be given with caution to breastfeeding mothers.
Atenolol tablets come in 25, 50 and 100 milligram strengths. Color, shape, and size of tablets vary by manufacturer. Tablets should be stored at room temperature between 68-77 F and protected from light. Occasional temperature variations from 59-86 F are permitted.
Cautions and Warnings — Abrupt discontinuation of atenolol can, as with any beta blocker, cause severe exacerbation of angina or result in myocardial infarction. Rebound or withdrawal hypertension has been reported and is well documented. Beta blocker therapy should be gradually tapered over two to three weeks rather than abruptly stopped. Atenolol should be used with caution in patients with severe bradycardia, second and third degree AV blocks or cardiogenic shock. While all beta blockers may exacerbate reactive airways, the cardioselectivity of atenolol produces less effect on the bronchi compared to non-selective agents. Impotence or sexual dysfunction rarely occurs with atenolol due to its cardioselectivity.
Studies on interactions between beta blockers and glucose control are conflicting. Some show that hypertensive patients treated with beta blockers are more likely to develop diabetes; others find no correlation between the two. Beta blockers should be avoided in insulin-dependent diabetics with frequent hypoglycemic episodes owing to a tendency of beta blockers to worsen, prolong or alter the hypoglycemic symptoms. Otherwise, use of beta blockers appears safe in diabetics. Any diabetic taking atenolol should be aware that beta blockers may mask symptoms of hypoglycemia such as sweating, tachycardia, and other sympathetic nervous system signs. Close monitoring of blood glucose is recommended during beta blocker therapy.
Use of beta blockers in patients with intermittent claudication was considered relatively contraindicated. The majority of studies, however, demonstrate that beta blockers do not worsen claudication symptoms in patients with mild to moderate peripheral arterial disease (PAD). Beta blockers should not be used in patients with severe PAD.
Important Side Effects and Interactions — Fatigue is the most commonly reported atenolol side effect, occurring in up to 26 percent of all patients. Dizziness has also been reported by up to 13 percent of patients. Other adverse reactions reported include hypotension (4 percent), diarrhea (3 percent), and nausea (3 percent) as well as cold extremities (2.6 percent), insomnia and depression.
There are 77 drugs specifically reported to interact with atenolol and most are either poorly documented or extremely uncommon. Two in particular are worth noting:
- Clonidine is an alpha andrenergic blocker also used to treat hypertension. In patients taking alpha blockers such as clonidine, discontinue atenolol several days before withdrawing the alpha blocker to prevent exaggerated rebound hypertension from unopposed alpha stimulation.
- Antacids containing aluminum, magnesium or calcium significantly decrease atenolol absorption. Atenolol should be taken two hours before or six hours after antacids.
Average Costs — U.S.
25 mg and 50 mg tablet (generic)
Patient cost: $0.10 and $0.12 each*
Large Hospital cost: $0.02 and $0.03 each
*($4.00 at Wal Mart® and Target for 1 month supply)
1. MICROMEDEXÒ Healthcare Series: Thomson Micromedex, Greenwood Village, Colorado (accessed October, 2007).
2. Albany Medical Center Pharmacy, Albany, New York.