Pharmacokinetics: Absorption (Nursing)

by Rhonda Lawes, PhD, RN

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    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.

    About the Lecture

    The lecture Pharmacokinetics: Absorption (Nursing) by Rhonda Lawes, PhD, RN is from the course Pharmacology and Implications for Nursing.

    Included Quiz Questions

    1. The movement of a drug through the body
    2. The effects of the drugs on the body
    3. The study of how drugs are absorbed
    4. The study of how drugs interact with each other
    1. Oral
    2. Intravenous
    3. Subcutaneous
    4. Topical

    Author of lecture Pharmacokinetics: Absorption (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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