Atenolol

Key facts

• Atenolol (sold as Tenormin and in generic tablets) is a cardioselective beta blocker. It slows the heart rate and reduces how hard the heart pumps, lowering blood pressure and easing chest pain.
• It is taken once or twice a day; blood pressure and heart-rate effects build over the first one to two weeks.
• Never stop atenolol suddenly. Abrupt withdrawal can cause rebound chest pain, a dangerous rise in heart rate, or a heart attack in people with existing heart disease; the dose must be tapered down gradually.
• Seek urgent care for a very slow or irregular pulse, fainting, or breathlessness that is getting worse.

What atenolol treats

Atenolol treats high blood pressure (hypertension), angina (chest pain from reduced blood flow to the heart), and abnormal heart rhythms such as atrial fibrillation, where it slows the heart rate. It is also used after a heart attack to reduce the chance of another one. It is not a fast-acting pain reliever and will not stop an angina attack already in progress.

How atenolol works

Atenolol blocks beta-1 receptors in the heart, the docking points that adrenaline and noradrenaline use to speed up and strengthen each heartbeat. With these signals dampened, the heart beats more slowly and with less force, lowering blood pressure and reducing the heart's oxygen demand.

Before you take it

• Use with caution or avoid if you have asthma or severe airway disease; even a heart-selective beta blocker can trigger wheeze or bronchospasm in some people.
• Tell your prescriber about diabetes (atenolol can mask a fast heartbeat, a warning sign of low blood sugar), a very slow heart rate, heart block, or decompensated heart failure.
• Kidney disease can cause the drug to build up, so your dose may need adjusting.
• Combining atenolol with other heart-rate-lowering medicines, such as verapamil or diltiazem, raises the risk of a dangerously slow heartbeat.

Side effects

Common effects include tiredness, cold hands and feet, dizziness on standing, a slower pulse, sleep disturbance, and mild stomach upset.

Stop and seek urgent medical care for any of these:

• A very slow or irregular heartbeat, or fainting.
• Chest pain that does not improve.
• Shortness of breath that is getting worse, or new wheeze.
• Swelling of the face, lips, tongue or throat.

Safety essentials

• The withdrawal rule is the key safety point: never stop atenolol abruptly. Stopping suddenly can trigger rebound angina, a sharp rise in heart rate, or a heart attack, so the dose must always be reduced gradually under medical guidance.
• Have your pulse and blood pressure checked regularly, and tell every prescriber you take atenolol before starting a new medicine.
• If you have diabetes, monitor your blood sugar closely, since atenolol can hide the usual warning signs of a low.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.