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Antiviral drugs for the flu

Rishi is a pediatric infectious disease physician and works at Khan Academy. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Rishi Desai.

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Video transcript

I'm going to quickly sketch out a flu virus for you-- something like this. And it has an envelope, so this is our little envelope. And on the inside of this envelope are eight chunks of RNA, so let's draw out the RNA. This is the genetic material. And this genetic material, among other things, codes for protein. And so one of the proteins here is sitting on the outside. I'm drawing it as if it looks like a little hand. And the reason I do that is because it reminds me that this H stands for hemagglutinin, but it basically holds onto sialic acid . And that's how it gets inside of little cells. And then there's another protein over here. And I draw these as a pair of scissors just to kind of remind me that this one nicks the sialic acid. This is called neuraminidase, and it nicks the sialic acid, and it helps it cut itself loose from the cell. And so it can move on to other cells- kind of helps with exiting. And I haven't actually been drawing this other protein. There's another one here. And I'm going to draw it now. This is called an M2 protein. But it's not actually found on all flu types. It's actually found on flu A, but actually not found on flu B. So this is a really important difference between flu A and flu B. And you'll see why, because one of the medicines that we use now to treat flu-- and yes, you heard me correctly, that we do have anti-viral medications. You probably heard from many people saying antibiotics only treat bacteria, not viruses, and that's true. But we have a special word for these other drugs that actually do treat viruses. And we call them anti-viral drugs. And there are couple of them. I'm actually going to write out some of the names. So this is called Amantadine or Rimantadine. And it's kind of easy to remember that they are in the same class because they share a lot of the same letters. And these two anti-viral drugs, they actually work on stopping or blocking the activity of this enzyme. And I'm just kind of drawing it like a little negative sign. But that's just to remind you that it blocks the M2. So if you know that flu B doesn't have M2, then you also know that these drugs then don't work against flu B. These drugs don't even work that well against flu A, because flu A has become quite resistant. So remember, resistance happens because there are little mutations. And it turns out that flu A has kind of a mutated form of M2, so that it actually doesn't get blocked by Amantadine or Rimantadine quite so easily. So unfortunately for us, that's bad news. And the CDC in 2012, 2013 have recommended not using these drugs because there's so much flu A resistance. So that's unfortunate, but the good news is that we actually have a couple of other drugs. So we have a drug called Oseltamivir, and related to it-- and you'll see with the spelling-- we have Zanamivir. And these, of course, share a lot of the same letters again. And these two actually block the neuraminidase. And this is actually in flu A and flu B. So that's good news, because it blocks both flu A and flu B. And let me actually just write that down, flu A and flu B. And that's important, right? So we have these two drugs, and one of them is a pill. This first one is a pill. And the second one is kind of an inhaled powder. So they're taken in different ways. And another important difference between them-- this is something that we have to just kind of keep in mind-- is that there are age restrictions. So you have to be a certain age to be able to take these medications. And they differ between the two drugs, and whether you're using it to treat, or if you're using it to prevent getting sick from the flu. There's a difference there too. So there are age restrictions that we just have to keep in mind. But overall, I'm pretty happy with the fact that at least we have these options if we need to treat someone that's very sick from the flu. So let's talk about that treatment then. So what if you have someone-- and this happens to me all the time where someone comes in kind of frowny faced because they're sick with the flu, and you're thinking, OK well, this person obviously needs treatment. So I'm going to write that at the top. They need some sort of treatment. And I guess the first question is, why would I treat this person? Of course, everyone's going to be frowny faced if they get the flu. So why am I treating this person? What makes them so special? Well, one thing that could make them special is-- let's say that they're high risk. Remember high risk groups in our society, in our community, include real young kids-- so let's say under two years old-- or older folks-- let's say people over 65 years old. It could be someone that's pregnant. That's another high risk group. Or it could be someone that has some sort of chronic disease. And that could be like a lung disease or asthma, any sort of chronic disease that makes them ill. Maybe their immune system isn't working. And that would be a group I would definitely consider treatment for. Now another group-- I'm going to put it just right below-- is let's say you have someone that's completely healthy-- young, healthy person, not pregnant. They still might get treatment if there's maybe severe disease. Let's say they get really, really sick. They're just feeling awful, and I'm worried about them, and they might need to be hospitalized. If they're very, very sick, or they get some sort of complication, or they're going to get hospitalization, anything like that, then this is a person, again, I would be careful with. And I would consider treatment. Let me bring up a little bit of space. So this is the kind of group that I would definitely consider treatment in. So what else should we think about or consider? Well, the next question, often, that comes up is how soon do you need to start treatment? When do you need to begin treatment? Or when do you start? And of course that answer's going to be as soon as possible. But a bigger range on that would be within two days. So really, if they've started getting symptoms a week ago, I might still be inclined to treat them. But I'd be more inclined if it had just started. What other questions or considerations should we just kind of go through? What about treatment? So how long do you treat them for? And generally speaking, it's about five days. So five days of either Oseltamivir or Zanamivir. And sometimes it goes a little bit longer, but usually it's just five days. That's kind of a normal course. So this is how I would manage someone that's being treated for flu. But of course, what if they're not being treated for it? What if they come in, and they're feeling fine? And we have to draw another face here. This is a smiley face, something like that. And I'm going to draw two. So let's say there's two. And we're going to deal with them separately. So let me actually draw a line between them, something like this. So we've got two more cases. Both are feeling fine, but they might need prevention. Another thing these drugs can do is prevent you from getting sick. So prevention is important as well. And let's say these folks are living in a home. Let me actually build a little nice house around my first smiley face person. And I'll do the same around this second smiley face person. And let's say this first person-- this person gets a visit from someone who's feeling flu symptoms. So this person comes to visit, and our friend, our smiley friend, is worried. They think, oh my gosh, now I'm going to get sick. So if they're high risk-- and we went through some of the categories-- actually, I should mention there are other categories, not just these that I listed. There are some others as well. But if they're high risk in some way, then I would consider giving them a medication like Oseltamivir or Zanamivir to prevent them from getting sick. Now this whole bit about severe disease or hospitalization-- this doesn't really apply because they're not sick. They're obviously not going to have severe disease or hospitalization already. What about this question of when would I start treatment. Well ideally, again, it's going to be within two days. So within two days of their exposure. We call the visit, or whoever kind of made them worry that they might get the flu, we call that the exposure. And so really you want to start treatment within two days. And you also want to start prevention within two days. So how long would you actually give them the medications for, to prevent them from getting sick? Well it really depends on whether or not they've had the vaccine. So let's say they've had the vaccine, the flu vaccine. And they were high risk. They got visited by someone, or had an exposure. For this person, I'm thinking I want to treat them for two weeks. Or give them two weeks of medications. And the logic is that if I kept them two weeks, then that basically covers them. And then after that, I would assume that the vaccine would kind of take hold. Because remember, the vaccine takes two weeks to really take full effect. So basically, I give them a medication during that period of time when the vaccine isn't completely protecting them. And then I expect their vaccine to kind of take over, and for the rest of the flu season, presumably, they should have good protection. So that would be my strategy. Now let's say that they can not take the vaccine, so no vaccine. And maybe this person has a severe allergy, or had a horrible reaction to the vaccine. For whatever reason, they cannot take the vaccine. Well in this person, if they can't take the vaccine, or don't have the vaccine, then for this person I would actually treat them for just one week. One week after exposure. So if the exposure happened, let's say today, I would basically-- and then let's assume it's not going to keep happening-- so one week after exposure would then make it next week, is when I would stop the medication. So in this scenario, I'm protecting them with the medication against getting sick from this exposure. But because they've had no vaccine, if they have ongoing exposures-- let's say they get exposed again to flu in three weeks-- then again they'd have to come back to me, and we'd have to do this all over again. So it really is ideal to have that vaccine in your system to keep protecting you and preventing you from getting ill. Now in this second scenario, let's say instead of having a visitor who's sick, let's say you've got people around you that are sick, living in the same place as you. Now this person is obviously in the home with a group of folks. So let's call that a group home. And what we call this scenario is basically an outbreak. So this person is living in an outbreak setting. And many, many people with flu are living together causing an outbreak to happen. We really are worried about other healthy people like our smiley faced friend from getting sick with the flu as well. So in this setting, who am I worried about? Who do I want to make sure gets medications to prevent them from getting sick? Well, we've got high risk people, again, living together. So if people are living together-- and this could be senior citizens, or could be a chronic care facility, or nursing home-- and really any kind of group setting where people are institutionalized and they're high risk, I'm going to be worried. And I want to make sure that we consider prevention with one of these medications, the Oseltamivir or Zanamivir. And do I have to worry about severe disease or hospitalization? Well, no, again because here specifically I'm talking about the healthy person who happens to be in an outbreak. So they're still healthy. They're not hospitalized. They don't have severe disease yet. So the whole idea is to make sure they don't get those things, right? And when would I want to treat them? Well, it's hard to really say within two days because that implies that something specific is happening. When in fact, during an outbreak, you just have constant exposure, right? I mean, everyone around you is sick. Let's say you go down to eat in the cafeteria. Everyone is sick. So when you're having constant exposure, we don't really think about within two days. It doesn't really make sense here. So here I would just kind of be worried in general about this person. And as far as treatment, you really end up just treating everybody. Vaccine or no vaccine, you treat everybody throughout the outbreak because the whole goal here is really to minimize the outbreak. You don't want people to have all the horrible consequences of flu. Remember, flu can kill people, and can cause hospitalizations. So to prevent all that, because it's a high risk group of people living together, you would really just treat throughout the outbreak. And even one week after the last case of flu is found. So here, unlike the scenario where you have just a single exposure, because you have so many people in an outbreak that are sick and kind of exposing each other, you basically just treat everybody with Oseltamivir or Zanamivir. So now you see we have a couple of anti-viral drugs, and you see when we can use them to treat folks, and also when we can use them to prevent folks from getting sick.