Atenolol is a drug in the class of beta-adrenergic blockers or antagonists. It is selective in its action with primary action on β1 receptors. This decreases the side effects experienced with use of Atenolol and makes it relatively cardioselective. Atenolol thus has decreased propensity to cause bronchoconstriction, and can be used relatively safely in diabetic patients as well as in those with peripheral vascular disease. However this selectivity in turn means that Atenolol cannot be used for many conditions for which Propranolol has been used, as it will have no effect on such conditions, e.g. anxiety states and essential tremor. The cardioselectivity of Atenolol is not seen when larger doses are used.
How Atenolol Works: Atenolol can be classified as the second generation of beta-adrenergic blocking agents. These drugs act selectively on the β1 type of adrenergic receptors. These receptors are present in larger quantities in the heart, which makes the action of Atenolol relatively cardioselective. Atenolol acts on the heart by decreasing cardiac output through a lowering of the heart rate and the force of cardiac contraction. This is accompanied by a decrease in cardiac oxygen consumption and reduced cardiac work. These actions form part of the mechanism by which Atenolol acts as an anti-hypertensive agent. The reduced need of the heart for oxygen also prevents and reduces episodes of anginal pain. The other mechanism that has been hypothesized is action on blood vessels and a lowering of the total peripheral resistance by adaptation. But this mechanism is likely to have a minor effect in the case of Atenolol since its primary action is on the heart. Like Propranolol, Atenolol similarly has membrane-stabilizing properties and is used in the treatment and prevention of arrhythmias. It decreases cardiac muscle automaticity and prevents ectopic foci from discharging impulses.
How To Take Atenolol: Atenolol is used in the management of hypertension, either as a single agent or in combination with other drugs. Atenolol is also used in patients suffering from angina pectoris to decrease the frequency of attacks and reduce their severity. After a patient has suffered a myocardial infarction, treatment with Atenolol helps to prevent further episodes and reduce the incidence of cardiac arrhythmias, which may be fatal. Atenolol is available as an oral tablet in the strengths of 25 mg, 50 mg and 100 mg. It is also available as an injectable solution at a concentration of 0.5 mg/ml for intravenous use. The usual starting dose of Atenolol in patients of hypertension is 50 mg/day as a single daily dose to be preferably taken in the morning, without relation to meals. The response should be judged by regular monitoring of blood pressure and the dose may be incrementally increased to a maximum of 100 mg/day taken as a single daily dose. If concomitantly any other anti-hypertensive drugs are used, a lower dose of Atenolol may be prescribed. A similar dosage regimen is used in patients of angina pectoris, with response measured in terms of exercise tolerance. When used in cases of myocardial infarctions, Atenolol is given as a 5 mg intravenous injection slowly and repeated after 10 minutes. An oral dose of 50 mg is used 10 minutes after the second IV injection and then continued as a 50 – 100 mg daily dose.
Precautions And Side Effects Of Atenolol: Atenolol should not be used in patients with heart blocks, renal or hepatic impairment, severe heart failure, asthma, or COPD. Though Atenolol is mostly cardioselective, due to the drug’s potential for causing side effects, one should be careful while using Atenolol for diabetics, patients with hyperthyroidism and peripheral vascular disease or Raynaud’s syndrome. Commonly observed side effects of Atenolol are fatigue, nausea and diarrhoea, cold symptoms, clammy hands and feet, and bradycardia (slow heart rate). Rarely seen with Atenolol are drowsiness, confusion, headache, cramping pain in the legs or hands, dry eyes, blurred vision, difficulty breathing, excessive bradycardia or cardiac rhythm disturbances, hypotension, and impotence.