Robert Downey Jr. announces on Golden Globes stage: 'I took a beta-blocker.' What do they do?

On Sunday, Robert Downey Jr. took home a best supporting actor Golden Globe for "Oppenheimer," but it was a throwaway line in his speech that got attention on social media:

"Yeah, yeah, I took a beta-blocker so this will be a breeze," he said when he took the stage.

Downey went on to call it a "most improved" award and thanked his wife Susan, who's "made an art out of extracting me from my comfort zone." But it was the beta blocker comment that people were buzzing about.

According to Mayo Clinic, beta-blockers are commonly used to reduce blood pressure and regulate heart rhythm. Though the Food and Drug Administration (FDA) have not approved them for the treatment of anxiety specifically, medical experts say the pills can be an option for those with event-related or performance anxiety like social phobia or stage fright. Just ask Khloe Kardashian! She has also raved about them.

Here's everything you need to know about beta-blockers:

What are beta-blockers, and how do they work?

Unlike antidepressants or benzodiazepines like Xanax, beta-blockers don't change a person's brain chemistry. Rather, they are prescription medications that temporarily block the body's physiological responses to anxiety like increased heart rate, tightness in chest or rapid breathing, depending on the type of beta-blocker used.

Dr. Sheldon Zablow, a psychiatrist based in San Diego, previously told USA TODAY beta-blockers are best for those who get anxious before specific events, like an important presentation or interview.

According to Zablow, beta-blockers are "fairly safe" with few side effects including fatigue and sexual dysfunction, though it is advised you avoid rigorous exercise if you've taken the medication. However, for those with pre-existing conditions like asthma or chronic obstructive pulmonary disease (COPD), beta-blockers can be dangerous and even lethal, according to Dr. Collin Reiff, a clinical assistant professor in the Department of Psychiatry at NYU Langone Health.

Is it safe?Khloé Kardashian says she takes Kris Jenner's beta-blockers.

"Beta-blockers like propranolol can lead to a bronchospasm in those with asthma or COPD," Reiff says. "It can also mask hypoglycemic episodes, so you have to be especially mindful if you have diabetes ."

Zablow explains, "You can take them situationally. If you can anticipate when you're going to be anxious and you take it before, it can help you get through the experience much easier," noting that they typically work within 10 minutes and effects last approximately three hours.

Zablow also cautions that beta-blockers are only a short-term solution for performance-related anxiety. 

"If someone has mild anxiety but it's particularly debilitating when you're in front of people or reporters, beta-blockers may be all that they need. But if someone has more severe anxiety that occurs almost all the time, that would require treatments like anti-depressants."

The bottom line? Beta-blockers might be right for some people but not everyone and you should check with your practitioner and seek help from a qualified medical professional if you need help coping with anxiety. 

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Contributing: Jenna Ryu