While shortness of breath is a possible side effect of metoprolol, it’s normally safe for those with asthma to take — under proper medical supervision.

All medications, no matter what they’re designed to treat, may cause side effects. In fact, a 2013 study found that almost 70% of drugs have the potential to produce between 10 and 100 adverse reactions.

However, some effects are more serious than others, so it’s important to be aware of them. In the case of the heart medication metoprolol, it may trigger asthma attacks in people with asthma. So what is this drug, and is it safe for those with asthma to take?

What is metoprolol?

Metoprolol is a type of beta-blocker. This form of medication is often prescribed to treat heart conditions such as:

However, it can also be used to treat tremors and migraine, explains Alex Toth, PharmD RPh, co-founder of InView Analytics, an inter-pharmacy collaboration platform.

There are two forms of metoprolol prescribed, depending on the patient:

  • metoprolol tartrate (Lopressor), an immediate-release formulation
  • metoprolol succinate (Toprol XL), an extended-release formulation

“The medication works by blocking the hormone called epinephrine [also known as adrenaline] at specific receptors in the body,” Toth states. This action then “causes the heart to beat with less force.”

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For people with respiratory disease or heart failure, taking metoprolol may cause respiratory symptoms to occur, says Aya Ozaki, PharmD, assistant professor of clinical pharmacy at the University of California, Irvine School of Pharmacy & Pharmaceutical Sciences.

Some rarer respiratory side effects of beta-blockers — including metoprolol — are shortness of breath, wheezing, and chest tightening. It’s also thought that some beta-blockers can obstruct breathing by narrowing the airways in the lungs.

However, for those who don’t have respiratory disease or heart failure, experiencing such symptoms “is rare,” Ozaki notes.

There’s no simple yes-or-no answer for this one. It largely depends on the severity of a person’s asthma and the type and dosage of beta-blocker prescribed.

There are two categories of beta-blockers: selective and non-selective. Selective beta-blockers only target beta-1 receptors in the heart muscles. Meanwhile, the non-selective variety targets beta-1 and beta-2 receptors in the heart and lungs.

Metoprolol is a selective beta-blocker. Ozaki says this means that “metoprolol works selectively in the heart with minimal or no effects on lungs [when taken] orally at doses of less than 100 mg in adults.”

As such, she continues, “the risk of experiencing respiratory problems is lower than with other beta-blockers.”

One study looked at data from over 35,000 patients with asthma and cardiovascular disease, of whom 14.1% had been given selective beta-blockers and 1.2% the non-selective type.

The researchers found that selective beta-blockers were “not associated with a significantly increased risk of moderate or severe asthma exacerbations.” On the other hand, non-selective beta-blockers were linked to a significantly increased risk of moderate to severe effects on asthma, even when taken at low doses.

Meanwhile, a meta-analysis of over 600 published reports found no associations between taking selective beta-blockers and severe or fatal asthma attacks.

That said, Toth states that beta-blockers should still be used with caution in people with asthma. “Many clinicians will avoid using any beta-blocker in patients with asthma due to the potential risk of developing wheezing or shortness of breath,” he adds.

While shortness of breath is a rarer reaction from taking beta-blockers, some effects are seen more often. According to Ozaki, these include:

But, Toth notes, “most of these side effects will decrease or go away as you continue to take the medication.”

Serious side effects can also occur if you attempt to come off the medication too quickly, shares Ozaki. “Stopping metoprolol (or any beta-blockers) abruptly is dangerous because it may increase the risk of a heart attack or other heart problems.”

It’s essential to work with your physician to devise a steady and monitored plan for withdrawal.

When to talk with your doctor

As is the case when taking any drug, you should speak to your physician if side effects persist or get worse.

Toth and Ozaki state you should immediately contact your doctor if you experience any of these symptoms:

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Metoprolol is a commonly prescribed beta-blocker — a type of medication used to treat various heart conditions.

Some of the rarer side effects of metoprolol (and other beta-blockers) include shortness of breath and wheezing. Those with asthma or respiratory disease are at higher risk of experiencing them.

Beta-blockers come in two forms, selective and non-selective, and non-selective has more of an impact on the lungs. As such, selective beta-blockers like metoprolol, which only influence receptors in the heart, are more often used for those with asthma.

Your doctor will determine whether metoprolol is safe for you, depending on your history and severity of asthma. If you’re already taking metoprolol and experience serious side effects, such as wheezing or a significant change in heart rate, you should contact your physician immediately.