What’s Atenolol’s Mechanism of Action? How This Beta Blocker Works

Atenolol (Tenormin) is a beta blocker that treats hypertension (high blood pressure) and stable angina (a type of chest pain). The medication is also FDA approved for use after a heart attack to lower the risk of death.

If you're prescribed atenolol, you may be curious about how it works, how long it takes to work, and how you'll know if it's working. In this article, we'll review atenolol's mechanism of action and what you can expect if you're prescribed this medication.

What is atenolol?

Atenolol is part of a group of medications called beta blockers. It comes as an oral tablet that's typically taken once a day.

Atenolol is FDA approved to treat hypertension, but it's not a first-choice medication for this condition. Other medications - including angiotensin II receptor blockers (ARBs), angiotensin-converting enzyme (ACE) inhibitors, and thiazide diuretics - are usually preferred over beta blockers for this purpose. These medications are typically better at decreasing blood pressure and cause less side effects than beta blockers.

Still, beta blockers can have benefits for treating hypertension if you have another heart-related condition, such as heart failure or angina. They can also be used if you've had a heart attack.

What's atenolol's mechanism of action?

Atenolol's primary mechanism of action is slowing heart rate. But if you're reading this article, you probably want to dig in a bit deeper into atenolol's mechanism of action.

Beta blockers like atenolol are so named because they block beta receptors, a type of binding site found throughout the body. To understand how atenolol works, it's necessary to know more about beta-1 and beta-2 receptors:

• Beta-1 receptors: While they're primarily found in the heart, beta-1 receptors are also found in areas of the body like the kidneys and fat cells. When they're activated, beta-1 receptors increase your heart rate and the force of your heart's contractions. When beta-1 receptors are blocked by beta blockers, your heart rate slows and the strength of your heart contractions decreases. This makes it easier for your heart to pump blood to the rest of your body. It also decreases your blood pressure.

• Beta-2 receptors:Beta-2 receptors are found in many places in the body, like the airways in the lungs and various types of blood vessels. When beta-2 receptors are activated, your airways and blood vessels dilate (widen) while your heart contracts (tightens) and your heart rate increases. When beta blockers block beta-2 receptors, the opposite happens. Your blood vessels constrict (narrow) and your heart relaxes.

Nonselective beta blockers block both beta-1 and beta-2 receptors. Others, like atenolol, block beta-1 receptors primarily. These are known as cardioselective beta blockers.

Cardioselective beta blockers may be preferred for people with certain health conditions that affect the lungs. This is because constricted airways can worsen symptoms of certain lung conditions, including asthma and chronic obstructive pulmonary disease (COPD).

Does atenolol start working immediately?

Atenolol typically starts working within 1 hour of taking it. And its effects usually continue to increase over the 4 hours following a dose. The effects of a single dose can last a full day.

The full effects of atenolol are usually seen within 1 to 2 weeks after starting treatment. This is why your prescriber will likely wait a couple of weeks before considering whether to change your atenolol dosage. They'll want to give your dosage time to work before they consider increasing it.

How do you know if atenolol is working?

Hypertension doesn't always cause symptoms. So you may not feel physically different after you start taking atenolol.

To determine whether atenolol is working, your prescriber may ask you to monitor your blood pressure and heart rate at home. Make sure to ask them what your blood pressure and heart rate goals are and how often to check.

If your blood pressure or heart rate is high, you may need a higher atenolol dosage. If it's too low, you may need a lower atenolol dosage. Low blood pressure (hypotension) is a possible atenolol side effect that can lead to dizziness and fatigue. More seriously, it can cause fainting and related injuries. So be sure to let your prescriber know if you experience side effects like severe dizziness.

Are there alternatives to atenolol?

As mentioned, atenolol and other beta blockers aren't considered first-choice medications for treating high blood pressure. Other medications are better at lowering blood pressure and they may be less likely to cause side effects like dizziness, fatigue, and hypotension

Examples of first-choice blood pressure medications include:

• ACE inhibitors, such as lisinopril (Qbrelis, Zestril)

• ARBs, such as losartan (Cozaar)

• Calcium channel blockers, such as amlodipine (Norvasc)

• Thiazide diuretics, such as hydrochlorothiazide (Microzide)

However, there are some situations in which atenolol is a good option for hypertension. For example, if first-choice medications don't decrease your blood pressure sufficiently, a beta blocker like atenolol may be a good choice. Another situation in which beta blockers may be effective is if you have hypertension and another heart-related condition, such as stable angina or a recent heart attack.

Comparing atenolol to other beta blockers

When comparing atenolol to other beta blockers, the decision on which is best comes down to several factors. A few factors are:

• The condition you're treating: For example, in people who need a beta blocker after a heart attack, metoprolol succinate (Toprol XL) and carvedilol (Coreg) are considered first-choice options because they're most supported by research for this use. And metoprolol succinate, carvedilol, and bisoprolol (Zebeta) are first-choice options for heart failure.

• If you have other health conditions: Cardioselective beta blockers like atenolol may be preferred over nonselective beta blockers in people with asthma or COPD.

• Whether you prefer to take your beta blocker once a day: Atenolol is taken once daily. Some beta blockers need to be taken 2 or 3 times a day.

• Whether you have liver or kidney problems: Unlike some beta blockers, atenolol isn't broken down by the liver. So it may be a good choice if you have existing liver problems. But atenolol is removed from the body by the kidneys. So if you have kidney damage, it may not be the best choice for you.