Muscarinic Antagonist: Atropine – Anticholinergic Drugs (Nursing)

by Rhonda Lawes, PhD, RN

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    00:01 Now, anticholinergic drugs - these guys are a little more evolved, right? They're a little more competitive.

    00:08 They're also known as parasympatholytic.

    00:11 Okay cool.

    00:12 Here's another word that we can break down.

    00:14 Parasympatho- means parasympathetic, but -lytic means boom! it's knockin it out.

    00:21 Parasympathomimetic means it's just like the parasympathetic system.

    00:26 Parasympatholytic means boom! It's against parasympathetic.

    00:31 So parasympatholytic, anti - against, muscarinic - that makes sense and muscarinic blockers.

    00:40 It's pretty much all the same thing so anti- is against, cholinergic - that makes sense because these drugs slide on into that cholinergic receptor.

    00:52 Remember muscarinic receptors are cholinergic receptors, they slide on in and they block anyone else from coming in.

    00:59 That's why they're against, they're blockers so I don't want to rush through that too quickly So when you see these terms, parasympatholytic drug - that means that the reaction is going to be against the parasympathetic nervous system more like the sympathetic nervous system.

    01:18 We can also call anti-muscarinic because anti is against or blocking the muscarinic receptors.

    01:25 or just plain old muscarinic blockers - they all mean literally almost the same thing.

    01:32 Okay, so anticholinergic produce the selective blockade of muscarinic receptors, it doesn't hit all the cholinergic receptors but it hits some of the muscarinic receptors Remember it competitively blocks the action of acetylcholine it means, "ha ha! i got there first, and you can't have my seat", right? It sits right in that muscarinic receptor.

    01:52 But the key is most muscarinic receptors aren't structures that are innervated by the parasympathetic nerves that's why there's such a close relationship between if you have an aganst that' s more of a parasympathetic response or if you have an antagonist or a blocker - it's more of a sympathetic response.

    02:11 Okay, so we're back to our formula here, right? How to study cholinergic drugs which we know also works with adrenergic drugs but today we're talking about cholinergic drugs.

    02:22 You have to know the receptors that are involved, you have to know what the name of the drug is so we know what receptors are involved and what the response is.

    02:30 Well, we're talking about atropine - that's our example drug.

    02:34 You can see that the muscarinic receptors are involved, they're located in the same places that we were talking about earlier.

    02:41 but because this is an antagonist, it's gonna be a parasympatholytic The other medication we talked about, bethanechol was a - oh, I'm sorry my tongue is getting twisted! Bethanechol is a parasympathomimetic, but this drug is an antagonist, it's a blocker so it acts more like the sympathetic nervous system.

    03:07 That's why it's sympathomimetic or mimicking the sympathetic nervous system.

    03:12 So you're gonna see opposite responses here, more like the sympathetic nervous system.

    03:18 Now look at what happens with this particular drug, of atropine.

    03:21 It will dilate the pupils.

    03:23 Hey, that'll be kinda cool for doing, looking at eye problems, right? or for trying to look into someone's eye, dilated pupils are really helpful.

    03:31 It's gonna dry up their mouths so they're gonna have less oral secretions, cool! That'll be good in surgery because we don't want you having a whole bunch of spit in your mouth when we've got you under general anesthesia.

    03:41 It's gonna increase your heartbeat.

    03:43 whoo! I really like that one.

    03:46 So you guys that are looking to go into critical care or ER, this is really important that you know this medication.

    03:52 We give it IV and it treats bradycardia - a heart rate that's too slow.

    03:58 Now, we would only give atropine for a slow heart rate if the patient was symptomatic.

    04:04 You can get some athletes and they're really like rock stars and they come in with a heart rate in the low 50's They're fine and their blood pressure's fine.

    04:11 But if we get somebody normally as hypertensive and has a heart rate in a high 80s and their heart rate dropped to below 50, we might be giving them atropine right away.

    04:20 This atropine is an antagonist.

    04:23 It's gonna block the parasympathetic relationship, right? The response? so we're gonna see an increase in heartbeat.

    04:31 So we use atropine for someone who's bradycardic, and symptomatic with it.

    04:36 The blood pressure is too low, they're feeling dizzy, they'll show us all kinds of symptoms.

    04:41 Now they'll open up the airways and will also decrease the activity of the stomach so somebody who's got really hypermotility of the stomach, this medication might have some application there.

    04:53 So that' why now when you look at the list of therapeutic uses of atropine, without looking back at your notes, so you can say, "Yeah, I understand why it treats bradycardia." Work through the rest of these - eye disorders, preanesthetic or surviving muscarinic poisoning.

    About the Lecture

    The lecture Muscarinic Antagonist: Atropine – Anticholinergic Drugs (Nursing) by Rhonda Lawes, PhD, RN is from the course Peripheral Nervous System (PNS) Medications (Nursing). It contains the following chapters:

    • Anticholinergic Drugs
    • Atropine
    • Therapeutic Uses of Atropine

    Included Quiz Questions

    1. It will block the actions of the parasympathetic nervous system to create actions more like those of the sympathetic nervous system
    2. It will block the actions of the sympathetic nervous system to create actions more like those of the parasympathetic nervous system
    3. It will activate the actions of the parasympathetic nervous system and activate the actions of the sympathetic nervous system
    4. It will block the actions of the parasympathetic nervous system and block the actions of the sympathetic nervous system
    1. It will dilate pupils, increase the heart rate, and decrease stomach activity
    2. It will constrict pupils, decrease the heart rate, and increase stomach activity
    3. It will constrict airways, decrease the heart rate, and decrease saliva production
    4. It will dilate the pupils, open airways, and increase stomach activity
    1. A client with symptomatic bradycardia
    2. A client with urinary retention
    3. A client with a small-bowel obstruction
    4. A client with orthostatic hypotension

    Author of lecture Muscarinic Antagonist: Atropine – Anticholinergic Drugs (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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