Pharmacokinetics: Absorption (Nursing)

00:01 Hi, welcome to this video on pharmacokinetics.

00:05 We're going to walk through each of the 4 major processes that are involved in moving that drug through the body.

00:11 Let's get started.

00:12 What is pharmacokinetics? Well, that's probably a word you haven't thought of before.

00:18 So let's break it down for you.

00:20 Pharmacokinetics is the movement of the drug through the body, from entry to exit.

00:25 And that means from the route that you took it to when it leaves the body.

00:30 That involves absorption, distribution, metabolism, and excretion.

00:37 So, as you're taking notes, as we begin this presentation, I want you to think about there's 4 main processes that we're going to discuss: how the drug is absorbed, how it's distributed, how it's metabolized, and how it's excreted.

00:50 So let's take a look at absorption.

00:52 Now, the definition of absorption is the movement of the drug from the site of administration to the bloodstream.

00:58 That's really simple, but there's lots of routes that you can take a drug with.

01:03 So, we're talking about the movement of the drug from the site that you give it to the bloodstream.

01:08 Now, this slide has an example of all the different ways that you can give a drug.

01:13 Pretty much if you have an orifice, we can give you a drug through it, right? Oral, sublingual, in your eyes, in your ears, and we can give it subcute, IM, IV, and other more personal routes.

01:26 But we're talking about absorption, which is from the point of entry till we get to the bloodstream.

01:32 Now, 2 factors you want to keep in mind is the rate of absorption and the amount of absorption.

01:38 The absorption rate is going to be higher depending on the speed of the effect, and the amount is going to determine the intensity of the effect.

01:45 So, the absorption rate will determine how quickly the patient feels the effect of the medication.

01:50 The amount that's absorbed will be the intensity of the effect the patient feels.

01:55 So let's look at things that impact drug absorption.

01:58 First of all, it's how fast the drug can dissolve.

02:02 The quicker the drug dissolves, the faster it's going to make it into the bloodstream.

02:06 The surface area also plays a role.

02:08 So, the larger the surface area, the faster the drug will make it into the bloodstream.

02:13 The quality of blood flow is also really important, the better the blood flow, the faster the drug will make it into the bloodstream.

02:20 The drug also has to have the ability to cross a cell membrane.

02:24 So, the more easily a drug crosses a cell membrane, the faster it will make it into the bloodstream.

02:31 Now, pH partitioning and drug ionization also plays a role.

02:34 Don't let that get you really excited.

02:36 It's not a big deal, but we're just talking about the pH in the stomach is 1.3, and it's 6 in the intestine.

02:43 And later on, we'll explain to you why that is so important and how it impacts drug absorption.

02:50 So, the first pass effect is something that I want you to keep in mind for oral medications.

02:55 Essentially, if you take a drug by mouth, it goes into your stomach.

02:58 It's got to go through the liver before it makes it into your bloodstream.

03:02 And a lot of the drug can be inactivated by the liver, and that's what we call the first pass effect.

03:08 Now although the first pass effect usually occurs in the liver, it can also occur in the lungs, the vasculature, the gastrointestinal tract , and other metabolically active tissues.

03:21 Now, that's the reason that oral medication dosages are much higher than IV medication dosages.

03:27 So keep that in mind.

03:29 First pass effect impacts oral drugs because the drug goes in the mouth, into the stomach, has to go through the liver, and a lot of the drug becomes inactivated in a first pass effect.