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Muscarinic Agonist: Bethanechol – Cholinergic Drugs (Nursing)

by Rhonda Lawes

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    00:01 Okay let's talk about cholinergic effects.

    00:04 Now this is part of the nursing lingo you wanna be familiar with, you want to know what anticholinergic effects are and cholinergic effects.

    00:11 So here's the deal, cholinergic drugs enhance the effects of acetylcholine Remember underline that word, "choline" again just to help you remember cause we're going after those cholinergic type of receptors So cholinergic drugs enhance the effects of acetylcholine and increase the actions of the parasympathetic nervous system, right.

    00:33 So cholinergic - I want you to connect to parasympathetic nervous system.

    00:37 Remember that's the rest and digest and sit back and have a big old fat meal, right? Yeah, lots of saliva and juices flowing and your gut is moving and you're real relaxed and your heart rate's slow - this is more of a parasympathetic reaction.

    00:54 Now an anticholinergic drug will competitively block the effects of acetylcholine.

    01:00 Yeah, competitive - that's what I mean.

    01:02 Those drugs are racing to get to that receptor because they want to get there first so they can fill up that receptor, sit down and claim their seat and now will allow acetylcholine to connect to that receptor.

    01:15 So they competitively block the effects of acetylcholine by sucking up that space on the receptor and not allowing acetylcholine to get in.

    01:23 That way you reduce the parasympathetic actions and increase the sympathetic ones Now, before we go on, let's break that down a little bit You know that you have these receptors that we're talking about the muscarinic receptors, you've got them on your heart, right? And we were talking about a parasympathetic response versus a sympathetic response Well, parasympathetic response - write "parasympathetic" on the top of your notes and write "sympathetic" on the top of your notes because i want to talk about the two types of differences.

    01:54 If we get a cholinergic type drug in there, it's gonna enhance the effects of acetylcholine Well that's the parasympathetic system so we're gonna see the heart rate slow down Now if we get an anticholinergic drug in there, remember it 's gonna block the effects of acetylcholine so we're not gonna have the parasympathetic effect of slowing down, we're gonna have the sympathetic effect of speeding up.

    02:22 So if I give a drug that's an anticholinergic drug that hits a receptor on your heart, you should see the heart rate increase.

    02:30 Okay, so that kinda helps you get a feeling for cholinergic versus anticholinergic, the difference between agonist and antagonists so that's just a quick review that help you to understand how we study these types of drugs Now let me give you an even better way to do it, okay.

    02:48 How to study cholinergic drugs Well you may have not thought you'll be doing that today but this is gonna be really helpful.

    02:55 Here's a tip - it also works for adrenergic drugs too.

    02:59 You look at the receptors that are involved, now we're talking about a drug so you look at the receptors that this drug involves, identify if the drug is an agonist or an antagonist and then we'll pretty much know what the expected response of the drug is.

    03:13 Woohoo! now you may not be celebrating but I am because this will help you to not have to memorize the list after list after list after list, this will help you really increase the effectiveness of your studying.

    03:25 So we're gonna look at some drugs and kinda use this formula to walk through it.

    03:30 You just have to know the name of the drug, the receptors that are involved - if it's an agonist or an antagonist and then we shall be able to expect the response of the drug.

    03:40 Are you ready? Okay.

    03:41 We're gonna talk about a drug that involves the muscarinic receptors, which that's cool because that's the title of this video series.

    03:49 So we look at muscarinic, it's going to be an agonist so I'm looking for a muscarinic agonist Now remember an agonist means it binds to a receptor, in this case the muscarinic ones and it activates that receptor to do what it's supposed to do.

    04:04 Okay, well how do I know what the job is? Well we gave you that chart right in this earliest part of the presentations to remind you what the muscarinic receptors are, where they're located and what their jobs are.

    04:16 So once we know it's a muscarinic agonist, we know they're located on these parts of your body and we know that we can expect the response of a drug like Bethanechol, we know what it can do.

    04:28 So this is the generic name, Bethanechol, now it hits the receptors and selectively activates muscarinic receptors that's an important point.

    04:37 Not every drug hits all of the receptors.

    04:41 So as you're studying these medications, you're gonna have to pay attention to which muscarinic receptor it hits.

    04:47 Now this drug in particular gives us some parasympathomimetic responses Now remember what those are.

    04:54 These are all the things that happens.

    04:56 So you got them right here, on the slide for you Eyes -that's what happen, heart - that's what happens, lungs - that's what happens but this one is selective so we don't get all of these responses with Bethanechol In fact, we use bethanechol because it activates the muscarinic receptors in the bladder, Okay we say selectively - those are the ones that goes after.

    05:19 So increases the bladder pressure, relaxes the smooth muscle of the sphincter and allows the urine to leave the bladder.

    05:26 Now if you feel like you hav to pee, this is really really important that you'd be able to do that, so it's therepeutic approved use for the relief of urinary retention That's what bethanechol is for because it goes after those muscarinic receptors, it acts like an agonist, it selects the receptors on the urinary bladder.

    05:46 Now we commonly use that for patients in post-partum or having difficulty urinating or for someone who has a neurogenic atony of the bladder Okay so think back through that, you know that we are talking about the muscarinic receptors It's an agonist, it specifically hits the ones on the bladder and that's why we use it to relieve urinary retention.

    06:08 Particularly after post-partum patients and neurogenic atony Okay so what are some things we want to be careful of? Well, theoretically, bethanechol can produce all of these side effects that you see there.

    06:21 All of these parasympathomimetic and that's a really long word to say that it mimics - mimetic the parasympathetic system, that's why it's called a parasympathomimetic I don't remember how to spell all of that but just remember that's why we're using these words and terminology to help you see how they all fit together So theoretically or technically, it can produce all of these side effects but really we take this as an old medications, it's pretty rare that it happens So it just selectively activates the muscarinic receptors on the bladder but just because it might happen, we try to be careful with the medication like bethanechol if the patient has asthma.

    07:02 Well, why is that a problem? Look over at that's possible, remember it's rare, that possible reaction to the parasympathomimetic, it might constrict the airways No for somebody with asthma, What about cardiac problems? Well, what does it do to the heart? Well it might slow down the heart rate.

    07:24 Okay, peptic ulcers - why would that be a problem? Well it could stimulate the activity of the stomach or an intestinal obstruction? same deal.

    07:34 So keeping in mind, this isn't a high risk with Bethanechol but in NCLEX world, we're always ultra ultra conservative.

    07:42 See when you know what those receptors do or what the possible reactions are, you know why we don't give it to patients with asthma, cardiac problems, peptic ulcers or an intestinal obstruction.


    About the Lecture

    The lecture Muscarinic Agonist: Bethanechol – Cholinergic Drugs (Nursing) by Rhonda Lawes is from the course Peripheral Nervous System (PNS) Medications (Nursing). It contains the following chapters:

    • Cholinergic Effects
    • How to Study Cholinergic Drugs
    • Bethanechol
    • Caution with Bethanechol

    Included Quiz Questions

    1. They increase the action of the parasympathetic nervous system
    2. They increase the action of the sympathetic nervous system
    3. They increase the action of the somatic motor system
    4. They increase the action of the central nervous system
    1. They decrease the action of the parasympathetic nervous system and increase the action of the sympathetic nervous system
    2. They increase the action of the parasympathetic nervous system and decrease the action of the sympathetic nervous system
    3. They increase the action of the somatic motor system and decrease the action of the parasympathetic nervous system
    4. They decrease the action of the central nervous system and increase the action of the peripheral nervous system
    1. It increases bladder pressure and relaxes smooth muscle to allow for urination
    2. It decreases bladder pressure and constricts smooth muscle to retain urine
    3. It increases bladder pressure and constricts smooth muscle to retain urine
    4. It decreases bladder pressure and constricts smooth muscle to allow for urination
    1. A client who is postpartum
    2. A client with asthma
    3. A client with peptic ulcers
    4. A client with cardiac dysfunction
    1. The receptors involved, where the receptors are located, and whether the drug is an agonist or an antagonist
    2. The receptors involved, where the receptors are located, and the therapeutic effect associated with each drug
    3. The receptors involved, the transmitter involved, and whether the drug is an agonist or an antagonist
    4. The transmitter involved, where the receptor is located, and the associated therapeutic response with each drug
    1. It will cause actions similar to those that occur when the parasympathetic system is activated
    2. It will cause actions opposite to those that occur when the parasympathetic system is activated
    3. It will cause actions similar to those that occur when the sympathetic system is activated
    4. It will cause actions opposite to those that occur when the somatic motor system is activated

    Author of lecture Muscarinic Agonist: Bethanechol – Cholinergic Drugs (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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