Atenolol is a beta-adrenergic blocking agent that blocks the effects of adrenergic chemicals, for example, adrenaline or epinephrine, released by nerves of the sympathetic nervous system. One of the important function of beta-adrenergic nerves is to stimulate the heart muscle to beat more rapidly. By blocking the stimulation by these nerves, atenolol reduces the heart rate and is useful in treating abnormally rapid heart rhythms. Atenolol also reduces the force of contraction of heart muscle and lowers blood pressure. By reducing the heart rate, the force of muscle contraction, and the blood pressure against which the heart must pump, atenolol reduces the work of heart muscle and the need of the muscle for oxygen. Since angina occurs when oxygen demand of the heart muscle exceeds the supply, atenolol is helpful in treating angina.
Atenolol is generally well tolerated, and side effects are mild and transient. Its side effects include:
dreaming, memory loss,
slow heart rate,
abnormal heart rhythm,
low blood pressure,
cold extremities, and
Atenolol can cause breathing difficulties in patients with asthma, chronic bronchitis, or emphysema. In patients with existing slow heart rates (bradycardias) and heart blocks (defects in the electrical conduction of the heart), atenolol can cause dangerously slow heart rates and even shock. Atenolol reduces the force of heart muscle contraction and can aggravate symptoms of heart failure.
The dose for treating high blood pressure or angina is 25-100 mg once daily.
Acute myocardial infarction (heart attack) is treated with two 5 mg injections administered 10 minutes apart. Ten minutes after the last injection, give 50 mg every 12 hours followed by 100 mg oral atenolol daily for 6-9 days. If atenolol injections are not appropriate, patients may be treated with 100 mg daily of oral atenolol for 7 days.