 I'm going to do a couple of videos here where I talk about anti-metabolite drugs. What an anti-metabolite is, is it's something that's going to be a competitive inhibitor of an enzyme that a microbe would use to do something. So the ones in this video, we're going to talk about the sulfonamide drugs like sulfon methoxazole, and we'll also cover trimethoprim. We'll cover isoniazid, which is an anti-microbacterial drug in a separate video. Real quickly, the sol-phones, just only one thing to know about them, the example there would be dapsone. It is really only used to treat Hansen's disease, which used to be called leprosy. So nothing to know much about that. But let's go and look at this picture here where we can see both sulfonamide and methoxazole and trimethoprim in action. So the sulfa drugs have been around a very long time since the 1930s. So these were actually in commercially used synthetic antibacterial agents. Again, not an antibiotic, because antibiotics have to be, technically, have to be a natural thing produced by microbes, but they've been around and in use longer than even penicillin, which we say is the first antibiotic. So the reason that the sulfa drugs, sulfonamide, and then you'll see it's called sulfon methoxazole usually, the reason they work is they block an enzyme called PABA, or para-amino-penzoic acid, what I say para-amino-benzoic acid, which microbes need to produce folic acid. So if you block the production of folic acid, then bacteria don't have folic acid. Without it, they can't make the pyrines and pyrimidines, which make the nucleic acid. So they can't make DNA, RNA, et cetera. So the reason this is a good selectively toxic drug is because we don't make folic acid. We get it from our diet. We eat it. We eat folate or we take folic acid supplementation. So we don't actually produce it in the same way that microbes do. Doesn't mean there aren't side effects. It is selectively toxic, but allergies are really common with sulfa drugs, even more common than your penicillin allergies. So this would be, this is the sulfonamide drugs here. Trimethoprim is going to block the same pathway just later on down the line, and that's why you often see them used together. So this is, as you can see here in the middle, trimethoprim is going to be a little bit later in the process. So the sulfa drugs are blocking the production of dihydrofolic acid, and then trimethoprim would come along and block the actual production of folic acid. So you usually use these two in combination. They are bacteriostatic, meaning that they use the bacteriostatic in that they inhibit the growth. If you use both together, though, you can block folic acid production enough where they can actually become bactericidal. So that's why you see usually the primary antibiotic that I talk about in class is a combination of both of these, and it's called trimethoprim sulfamethoxazole. So these two drugs working together. It's a pretty good example of a drug combination or a synergy. When I think of synergy, I always think one plus one equals three. If you put the two drugs together, you can use way less of both of them. So that's what I mean by kind of a synergy example. One last use, you might see like sylvanine, silver sulfadiazine. That's an example of a sulfa drug that can be used with burns. So these are the most important anti-metabolite drugs, the sulfa drugs, which are a very broad spectrum, can be used in a wide range of things unless you're allergic to them. And here you can see why. They're blocking a metabolic process that bacteria need that we don't. So they are selectively toxic. All right, I hope this helps. Have a wonderful day. Be blessed.