How does medicine know where to go in the body to fight disease? For example a throat infection vs a stomach infection vs an infected cut on your foot?
In: Chemistry
I’ve wondered the same thing, especially with the new drug coming out that’s supposed to help you regrow teeth. Is that going to regrow all of them? Just specific ones?
It doesn’t. When you ingest medicine, it dissolves in your stomach for your body to carry around much like any other nutrient.
Instead, some modern medicines will be given certain chemical compounds designed to stick to the kind of tissue that appears in the part of the body it’s meant to help. For example, if you have a medicine that’s supposed to help with strep throat, it will be chemically designed in such a way that it will very effectively bond with the tissue in your throat while also not doing so with any other tissue. Thus, no matter what direction the body takes it, it will hopefully continue flowing until the body finally sends it past the throat, where it will stick to the tissue and end it’s journey. This means at least most of the medicine will be able to do it’s job right.
This answer is actually pretty simple in most cases: it doesn’t.
The medicine you take by mouth will get digested and then enter the blood steam where it circulates throughout your whole body (but maybe not your brain… It’s hard to get medicine into the brain).
If you have a throat infection, you might see the buildup of bacteria on your throat, but they aren’t just on the outside of you, they are inside of you, too. By circulation of antibacterial medicine throughout your whole system, you kill off that bacteria (and other bacteria) everywhere.
Notice I said and other bacteria, as well… This is why most antibiotic medication will have a warning to take it with food, because it typically causes an upset stomach. That upset stomach is caused by multiple factors, but one of them is the antibiotic medication killing the microbiota in your digestive tract.
Everything that I just said above, for the most part, is specifically for oral medication (stuff you take by mouth).
The rules change a little bit when you’re talking about topical ointments, eye drops, or injectables. It gets even crazier when you start talking about some types of anti-cancer drugs, that are designed to essentially build up in tumor tissue, but not stick around in the rest of your body. I’m going to skip those explanations for the moment, because doing that in an ELI 5 fashion is going to be tricky.
Your question is generically about medicine, but I guess you meant antibiotics, so I’ll answer to that:
1. In general, medicines are absorbed by the gut and reach the bloodstream. They’re carried by the blood to every part of the body. This is how they generally reach every area that might be infected
2. Each antibiotic has a different modus operandi. Some dissolve the cell wall of the bacteria (humans, being animals, don’t have cell walls). Some would prevent the bacteria from reproducing, by disrupting certain chemical reactions that the bacteria need to replicate. Some would make it easier for our immune system to find them by binding to a protein in its cell wall.
3. Depending on their nature of action, certain antibiotics work very well in certain infections (gut infection vs upper respiratory tract infections, for instance)
4. For resistant microbial strains, we can use a combination of multiple antibiotics, or use a higher generation antibiotic which the microbe isn’t yet resistant to (cephtriaxone or ceftaroline, for instance)
It doesn’t. The antibiotics go through your entire body. Most antibiotics work by penetrating the cell wall of the bacteria that is causing the infection. You take a pill (or sometimes and IV infusion) and the antibiotics get into your blood stream. When they come across the bacteria, a chemical reaction occurs that kills the bacteria. But it does not “know where to go.” It just goes everywhere. This is why stomach problems are a common side effect of antibiotics. Your gut relies on a robust variety of bacteria living inside of it to help you digest food. Antibiotics inherently weaken those bacteria colonies and some people get sick as a result of it. The goal on developing antibiotics is to develop kinds that tend to work really well on the infectious microbes and not very well on the good bacteria in your body.
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