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Last week, the opioid epidemic was declared a ‘public health emergency’ in the United States, but what are opioids, and why is the way they interact with the human brain potentially so dangerous?
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Last week, the opioid epidemic was declared a ‘public health emergency’ in the United States — something advocates have been pushing for a while.

Because at this point, experts agree that America is in the middle of an opioid crisis. According to the CDC, around 90 Americans die from opioid overdoses every day That's about as many as those who die in car crashes.

There are all kinds of different factors that led to this crisis. But the main reasons have a lot to do with what these drugs are, how they reduce pain, and why they’re so addictive. First, some terminology.

You hear people throwing around words like opioids and opiates, not to mention heroin, oxy, and fentanyl. But those mean different things. Opioids are any drug that acts on opioid receptors on your cells.

Opiates are essentially the same, but they’re made from the poppy plant. Yep, the plant that gives us lemon poppy seed muffins also makes opium and morphine. So opiates are natural, while opioids include both natural and synthetic drugs.

For our purposes, what matters is that they all bind to opioid receptors on cells around your body, like in your brain and spinal cord. These receptors come in different shapes, like mu opioid receptors. And when opioids bind to receptors, it makes it harder for neurons to send along signals that get interpreted as pain.

This happens in the spinal cord, where peripheral nerve cells pass on incoming signals. And it happens in the brain, where neurons in a region called the periaqueductal gray prevent cells from releasing neurotransmitters, which are basically chemical messages. All this means opioids are really good pain relievers.

And in the 1990s, because of a combination of factors including misrepresented research, doctors started prescribing more painkillers like oxycodone and hydrocodone to try to treat pain. But opioid receptors are also in reward centers of the brain, and binding to cells there can create euphoria, which is that ‘high’ feeling. That’s what makes them addictive.

Plus, your body builds tolerance to them pretty quickly, so you need more of the drug to control the same amount of pain. You can also become physically dependent, experiencing symptoms of withdrawal if you stop taking the drug. Since neurons get used to the opioids, they become more active to compensate for the drug suppressing signals.

And if it’s no longer there, the cells become way more active than normal. So you can become agitated, anxious, or feel like puking. Addiction, on the other hand, is a psychological condition where you seek out the drug despite the damage it does to your life.

While physical dependence is common with addiction, a person doesn’t have to be dependent to become addicted and vice versa. With the opioid epidemic, it’s thought that many people who originally took the drugs as prescribed started to take more. In other words, they began abusing them.

And when pills became too expensive or difficult to get, they turned to heroin, an opioid made from morphine, which was more readily available. Regardless of the source, the addiction can turn deadly because of the other physiological effects of opioids. That’s because opioid receptors aren’t just in areas of the brain that control pain; they’re also in the parts that control breathing, like the brainstem.

And when they block signaling there, opioids slow down and can even stop breathing. Doctors call this respiratory depression, and it’s usually what kills people who overdose. Fortunately, we now have some ways to counteract overdoses.

For instance, naloxone can be injected or squirted up someone’s nose and, within minutes, seemingly bring people back from the dead. It’s actually an opioid, too, since it binds to opioid receptors. But unlike heroin or prescription painkillers, which are agonists, naloxone is an antagonist.

That means that when it binds to a receptor, it doesn’t turn on any of the usual effects. Instead, it acts as a blocker. Naloxone works so well because it binds to opioid receptors more strongly than the overdosed drug.

So it can flood your system and prevent the drug from binding. Problem is, you need to treat someone with naloxone pretty fast. It doesn’t always take long after an overdose for them to stop breathing.

And that’s especially true if they’ve taken one of the stronger synthetic opioids, like fentanyl. Fentanyl is a prescription drug that’s around 50-100 times stronger than morphine. Because of its structure, it can cross a protective membrane called the blood-brain barrier more easily, which means your brain can get flooded with the stuff faster.

Lately, illicit versions of it have been added to heroin and other drugs sold on the street. And other, fentanyl-like drugs are even more powerful, like carfentanil, which is used to tranquilize elephants. Not only do these drugs cause faster overdoses, but they also need more antidotes to counteract the effects.

So even if the person is given a treatment like naloxone in time, there might not be enough on hand to save them. Deaths from overdoses have spiked in recent years, and as the problem has gotten worse, experts have been trying to figure out how to deal with it. For the most part, doctors are starting to cut back their prescriptions of opioids, which should help reduce the number of people who go on to develop addictions.

And researchers are working on finding opioids that can knock out pain without all the dangerous side effects. Some groups, for example, are studying drugs that are closer to the opioid peptides our bodies make, which may bind to receptors in more specific ways. But in the meantime, there are already a lot of people out there with substance abuse disorders, and helping them get into treatment is a whole other challenge.

So, there’s still a lot of work to do. Thanks for watching this episode of SciShow and thanks especially to our President of Space, SR Foxley! We really appreciate your support.

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