Pharmacokinetics: Metabolism (Nursing)

00:01 Metabolism is the chemical alteration of the drug.

00:04 We also call it biotransformation— that sounds a lot fancier, but that’s really what’s going on.

00:09 It takes the drug and transforms it.

00:12 Most of it occurs in the liver using the P450 and we’ll talk about that in just a minute, but I want you to have solid, in your mind, that metabolism is the chemical alteration or the biotransformation of the drug.

00:25 Most of it happens in the liver using that P450.

00:28 So let’s look at what happens when a drug is metabolized because it’s all over the map what can happen.

00:33 You might have faster excretion of the drug by the kidneys because the liver takes a drug that’s lipid soluble and makes it water soluble so the kidneys can excrete it in your urine.

00:44 It can also inactivate some drugs so that helps the body get rid of things or there’s usually a reason we want that drug to be inactivated.

00:53 Now bioactivation of “prodrugs”— it means it takes an inactive drug and makes it active— so right there, we might be able to change it into a form that we can get it out of the body quicker— take it from lipid to water soluble— it can either inactivate a drug or activate a drug.

01:12 Now the toxicity levels can also be increased or decreased, so when I said it’s all over the map, I wasn’t kidding, right? It can have all kinds of reaction because the liver is amazing in what it can do.

01:24 So I might have a risk for increased or decreased toxicity.

01:27 If it inactivates the drug, then I’m going to have less risk for toxicity.

01:31 If it activates the drug, then it might increase my risk for toxicity.

01:35 So when you’re thinking about metabolism— it happens mostly in the liver.

01:40 The biggest concept is it can take lipid-soluble drugs and make them water soluble, it can inactivate drugs or activate drugs.

01:49 Now that cytochrome P450 system— this is really killer— because it’s a microsomal enzyme system, but it is a group of 12 closely related enzyme families.

01:59 It is amazing at what it can do.

02:01 It metabolizes drugs and endogenous compounds.

02:04 So endogenous just means those are things that my body makes by itself— we’re focusing on what the P450 system does to drugs, but it also has some really cool factors in the rest of your body.

02:16 So, if it takes a “prodrug,” then it can have bioactivated in the liver and then it can be distributed out to the rest of the body to do what we need it to do.

02:25 So the cytochrome P450 system is something that’s worth noting in your notes.

02:31 So pause and just see if you can kind of recall what the key concepts are.

02:43 So the most important things you want to remember about the P450 system is that it is 12 closely related enzyme families and it is amazing at what it can do with activating “prodrugs.”