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Atenolol information

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Atenolol

Atenolol is a drug belonging to the group of beta blockers, a class of drugs used primarily in cardiovascular diseases. Introduced in 1976, atenolol was developed as a replacement for propranolol in the treatment of hypertension. Hypertension is a clinical condition in which the arterial blood pressure in rest exceeds constantly 140/90 mm Hg (as defined by the World Health Organization). Hypertension is a risk factor for stroke, myocardial infarction (heart attack), and serious renal damage.
Propranolol is known to readily cross the blood-brain barrier (BBB) and can pass into the brain, causing side-effects such as depression and nightmares; atenolol was specifically developed to be unable to pass through the blood-brain barrier in order to prevent this effect.
Whilst atenolol, the most widely used beta-blocker in the United Kingdom, was once first-line treatment for hypertension, the role for beta-blockers in hypertension was downgraded in June 2006 in the United Kingdom to fourth-line as they perform less well than other drugs, particularly in the elderly, and there is increasing evidence that the most frequently used beta-blockers at usual doses carry an unacceptable risk of provoking type 2 diabetes.

Indications

Atenolol (trade name Tenormin) can be used to treat cardiovascular diseases such as hypertension, coronary heart disease, arrhythmias, and treatment of myocardial infarction after the acute event. Patients with compensated congestive heart failure may be treated with atenolol as a comedication (usually together with an ACE inhibitor, a diuretic and a digitalis-glycoside, if indicated). In patients with congestive heart failure, it reduces the need for and the consumption of oxygen of the heart muscle. It is very important to start with low doses, as atenolol reduces also the muscular power of the heart, which is an undesired effect in congestive heart failure.
Atenolol is a so-called beta1-selective (or 'cardioselective') drug. That means that it exerts greater blocking activity on myocardial beta1-receptors than on beta2 ones in the lung. The beta2 receptors are responsible to keep the bronichal system open. If these receptors are blocked, bronchospasm with serious lack of oxygen in the body can result. However, due to its cardioselective properties, the risk of bronchospastic reactions if using atenolol is reduced compared to nonselective drugs as propranolol. Nonetheless, this reaction may also be encountered with atenolol, particularly with high doses. Extreme caution should be exerted if atenolol is given to asthma patients, who are particularly at risk; the dose should be as low as possible. If an asthma attack occurs, the inhalation of a beta2-mimetic antiasthmatic, such as hexoprenalin or salbutamol, will usually suppress the symptoms.
Provisonal data suggests that antihypertensive therapy with atenolol provides weaker protective action against cardiovascular complications (e.g. myocardial infarction and stroke) compared to other antihypertensive drugs. In particular, diuretics are superior. Propranolol and metoprolol might also be better alternatives. However, controlled studies are lacking (CARLBERG, B. et al.: Lancet 2004; 364: 1684-9).

Side effects

Atenolol causes significantly fewer central nervous system side effects (depressions, nightmares) and fewer bronchospastic reactions, both due to its particular pharmacologic profile.
It was the main beta-blocker identified as carrying a higher risk of provoking type 2 diabetes, leading to its downgrading in the United Kingdom in June 2006 to fourth-line agent in the management of hypertension.

Overdose

Symptoms of overdose are due to excessive pharmacodynamic actions on beta1 and also beta2-receptors. These include bradycardia, severe hypotension with shock, acute heart failure, hypoglycemia (= low blood sugar) and bronchospastic reactions. Treatment is largely symptomatic. Hospitalization and intensive monitoring is indicated. In early cases emesis can be induced. Activated charcoal is useful to absorb the drug. Atropine will counteract bradycardia, Glucagon helps with hypoglycemia, Dobutamine can be given against hypotension and the inhalation of a beta2-mimetic as hexoprenalin or salbutamol will terminate bronchospasms.