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Drugs that treat heart failure are also prescribed for anxiety? What's up with that?

Hosted by: Hank Green
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Sources:
http://www.ncbi.nlm.nih.gov/books/NBK47168/
https://www.drugs.com/drug-class/beta-adrenergic-blocking-agents.html
http://www.nature.com/scitable/topicpage/gpcr-14047471
http://www.nhs.uk/Conditions/Beta-blockers/Pages/Introduction.aspx
http://www.nimh.nih.gov/health/publications/panic-disorder-when-fear-overwhelms/index.shtml
http://www.currentpsychiatry.com/home/article/performance-anxiety-how-to-ease-stage-fright/40ca615e9165e7348a2870639197051c.html
https://www.bhf.org.uk/heart-matters-magazine/medical/drug-cabinet/beta-blockers
[SciShow intro plays]

Hank: Beta blockers are a class of medications prescribed for a few different reasons — mainly heart conditions and anxiety. But how does a drug that treats heart failure also help with anxiety? Well, when it comes down to it, the symptoms of heart failure and the physical anxiety response aren’t so different.

The beta in “beta blockers” refers to beta-adrenergic [add-ren-ER-jick] receptors, part of the sympathetic nervous system that controls the “fight-or-flight” response. When activated, it prepares your body for action: your heart thumps, your pits get all sweaty, and your pupils dilate.

You probably know the feeling as the adrenaline rush, but sometimes the sympathetic nervous system becomes overactive or erratic, leading to high blood pressure, tremors, or abnormal heart rhythms. The sympathetic nervous system also acts up when you’re anxious, which is why you might get that same heart-pumping, sweaty-pits feeling.

And during a panic attack, the sympathetic nervous system basically maxes out. It’s not uncommon to get heart palpitations and shortness of breath. The responses are so similar that when they have a panic attack for the first time, a lot of people think they’re having a heart attack.

There’s a whole mechanism that triggers the sympathetic nervous system: Adrenaline and a similar molecule called norepinephrine [nor-ep-in-EFF-rin] are chemical messengers that beta-adrenergic receptors are set to pick up. The receptors are large proteins that straddle the membranes of cells that need to detect this signal and respond accordingly — like heart and skeletal muscle. The receptors’ ability to change shape allows them to transmit the message from a few molecules outside the cell, and cause major changes inside.

When adrenaline or norepinephrine comes along and binds to a beta-receptor, the receptor shifts and twists to accommodate it. This shift bumps off a smaller protein that was tucked up against the inside edge of the receptor. Now free, this smaller protein activates enzymes, kick-starting a chemical chain-reaction of events that spreads throughout the cell, eventually leading to that adrenaline-rush feeling.

Beta blockers work by, well, blocking this system. The drugs have similar structures to adrenaline and norepinephrine, so they can slot inside the same place on the receptors. But the beta blockers don’t fit snugly enough to cause that shift in the receptor that triggers the reaction. So they just sit there for a few hours or so before gradually dissipating away — and in the meantime, signals from adrenaline and norepinephrine won’t get transmitted as effectively.

By slowing the sympathetic nervous system, beta blockers can help manage heart conditions like high blood pressure and irregular heartbeat, but they can also treat the physical symptoms of anxiety. They don’t treat the underlying causes of anxiety. But they can physically calm your body down. That’s also why some people use beta blockers as performance enhancers. Like if they want to display more confidence during a speech, or cool their nerves before an interview.

Beta blockers can come with risks and side effects, though. They can disrupt sleep, and cause nausea, abdominal pain, or shortness of breath. They’re particularly dangerous for people with asthma or certain heart issues. Plus, they can interfere with other drugs, and coming off them too suddenly is risky. But when used properly, they can help maintain both heart and mental health by soothing the sympathetic nervous system.

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