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Antibiotics are one of the greatest medical innovations ever, responsible for saving something like a gazillion lives. But today, we're worried about overusing them, and there are concerns that one day they won't really work anymore. There are lots of misconceptions about antibiotics, and in this week's episode we're going to tackle a lot of them.

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John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen - Graphics
Antibiotics are one of the greatest medical inventions of all time. They’re responsible for saving untold numbers of lives but today, as with many medical interventions, we’re worried about using too much of them as opposed to too little. There are also many misunderstandings and myths about antibiotics. We’re gonna hit on a lot of them speed round style in this episode of Healthcare Triage.


Antibiotic Myth #1: Antibiotics kill germs that cause colds or the flu.

No! Antibiotics kill bacteria. Different types of antibiotics kill different types of bacteria. But the flu and colds are caused by viruses. Antibiotics don’t kill viruses. Don’t tell me how you got better on antibiotics when you had a cold. Was it part of a randomized controlled trial? No! Cos if it was, you would have seen that people who didn’t take the antibiotics got better too. That’s the point.

Antibiotic Myth #2: You need and antibiotic if your snot is green.

No! Let’s start with some basic facts. What makes snot turn green? When you have an infection, the body sends neutrophils, which are a type of white blood cell, to fight the germs. So if you have an infection in your nose it’s likely there are more neutrophils present in your nasal passages than usual. These cells work by eating the germs that make you sick. Once they’ve swallowed them, they keep them in what serves as their stomachs and then they digest them. One of the enzymes that the white blood cells use most often to digest the invader germs is called myeloperoxidase and myeloperoxidase has a fair amount of iron in it. Stay with me, I promise this is important.

Once the neutrophils get full of digested germs they burst. Then the iron in the myeloperoxidase gets mixed into the surrounding stuff in your nose and when you mix iron into that stuff, guess what color it turns? Green. No, the color green. Notice I said nothing about bacteria. That’s because this works exactly the same no matter what the germ is. So you may have green snot with a bacterial infection but you could also have it with a viral infection. The bottom line is that the green does not tell you if it’s bacteria and only bacterial infections need antibiotics.

Antibiotic Myth #3: Birth control doesn’t work if you’re on antibiotics.

The concern for those who believe this myth is that somehow antibiotics interfere with a woman’s absorption of the hormones in the birth control pill. This has been studied extensively. For instance, one study looked at hundreds of women in three dermatology practices with a history of long term use of antibiotics and birth control pills together. There was no statistically significant difference between how many women got pregnant in the group on both antibiotics and birth control pills and the control groups where women were taking just birth control pills.

Remember, birth control pills fail at least 1% of the time even under ideal conditions. That’s why people think they fail when they’re on antibiotics but it’s not the antibiotics. Now there’s a tiny amount of evidence that one antibiotic called rifampin, which is a drug usually used for tuberculosis, may make birth control pills less effective. A study looked at thirty women who were on both the antibiotic rifampin and birth control pills and found that while the level of the hormone in their blood was lower than we might have liked, still none of them got pregnant. There’s no evidence for antibiotics in general making the pill less effective. Period. Oh, that, that was bad.

Antibiotic Myth #4: Once you’re on antibiotics, you’re no longer contagious.

I think school systems invented this myth. They send your kid home because he’s a “danger” to all other kids like Typhoid Mary or something but as soon as you’ve got him on antibiotics then sure, let him come back. First of all, the time period when you’re contagious varies according to what infection you have. For many viral infections, especially the viruses that cause most of our colds and the flu, antibiotics will never ever make you less contagious. Even more problematic is that sick people are often contagious before they show any symptoms. When you’re infected with a virus you typically shed or spread it for at least a day or two before you have any idea that you’re sick. The virus is in anything coming out of your mouth or your nose at that time even before you’re coughing and sneezing. You shed virus when you’re actually sneezing and you shed virus even when you're starting to feel better. You’re a nightmare!

Bacteria on the other hand aren’t usually as contagious. You know why doctors treat strep throat? It’s not cos primarily they think it will make other people less likely to get infected. It’s because back in the day they were trying to prevent rheumatic fever. Now it’s not even clear we’re doing that because the strains of strep have changed and I’m, I’m not even gonna start taking about that because it’s another story and we’re doing speed round. There are very few scientific studies that tell us how long you’re gonna be contagious. The idea of 24 or 48 hours is roughly based on how fast we think antibiotics decrease the load of bacteria within the body. For some conditions though, you could still be contagious with only a small amount of bacteria around even after you’ve been on antibiotics for a while. For other conditions, a person might never have been very contagious or the period of being contagious might have passed even before they started the antibiotics. Some infections are still contagious as long as you have a rash or have a cough where as others are not. But the idea that once you’re on antibiotics you’re safe for others is just crazy. Well, not literally crazy, figuratively ah, all right, next!

Antibiotic Myth #5: It’s OK to take someone else’s antibiotics.

Nope! I just told you that certain antibiotics kill certain bacteria. If you don’t have the same bacteria, the antibiotic won’t work for you. It’s very likely that you have no idea what bacteria you’re infected with. Ask your doctor, don’t assume.

Antibiotic Myth #6: You can stop taking your antibiotic when you start to feel better.

Remember when I said you could feel better and still be contagious. That’s cos you can feel better and still be infected. Take all the antibiotics.

We’re out of time, but we’re not done with antibiotics. We still need to talk about resistance and MRSA and superbugs. We’ll get to those other things soon.