Pharmacology, part 26: Nervous System Medications for Alzheimer's, Myasthenia Gravis, Parkinson's
by Cathy Parkes March 16, 2021 Updated: December 29, 2021 7 min read
In this article, we give a brief overview of Alzheimer's, myasthenia gravis and Parkinson's disease, then cover the medications use to help treat these diseases—cholinergics, anticholinergics, and dopamine agonists. The Nursing Pharmacology video series follows along with our Pharmacology Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.
When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!
Cholinergic for Alzheimer's - Donepezil (Aricept)
Donepezil is a cholinergic agent that is sometimes used in patients who have Alzheimer's. It may improve a patient's memory, their cognition, and their ability to perform their activities of daily living (ADLs).
It's important to note that this medication does not cure Alzheimer's disease — it just helps to improve their memory and cognition.
Don’t forget things (like your Pez dispenser) when you take donepezil.
What is Alzheimer's?
Alezheimer's is a brain disease with gradual, irreversible dementia, resulting in memory problems, judgment issues, and changes in personality.
Alzheimer's is an important disease you will learn about in Med-Surg and/or gerontology, and it is covered in our Medical-Surgical flashcards for nursing students, including pathophysiology, risk factors, signs and symptoms, the three stages, diagnosis, treatments, nursing care, and home safety instructions. We also cover this in the Gerontology section of our Fundamentals of Nursing Flashcards!
It is theorized that Alzheimer's is associated with the loss of cholinergic neurons that produce acetylcholine.
Mode of action
Donepezil helps to increase acetylcholine by inhibiting the action of cholinesterase, which is an enzyme that breaks down acetylcholine.
Side effects of donepezil can include headache, diarrhea, and nausea.
If you have a patient with Alzheimer's taking donepezil, remember that it is administered at night.
Cholinergics for myasthenia gravis - Neostigmine (Bloxiverz), pyridostigmine (Mestinon)
Neostigmine and pyridostigmine are cholinergic medications used to treat myasthenia gravis; they can help improve the strength and mobility in patients who have myasthenia gravis
What is myasthenia gravis?
Myasthenia gravis is an autoimmune disorder that causes severe muscle weakness, characterized by periods of exacerbation and remission.
Myasthenia gravis is also covered in our Medical-Surgical flashcards, including pathophysiology, signs and symptoms, diagnosis, treatment options, and nursing care tips to remember.
Mode of action
Neostigmine and pyridostigmine's mode of action is to increase the amount of acetylcholine at the receptor sites by inhibiting the action of cholinesterase, which is an enzyme that breaks down acetylcholine
Stig (race car driver) pulls up and blocks cholinesterase with his car, which prevents the breakdown of ACh. Most contain “stig”.
You may remember at several points in this series that we have covered the side effects of anticholinergic medications and that those medications are drying — can't pee, can't spit, etc. Well, cholinergic medications have the opposite effect—increasing moisture. Side effects of cholinergic medications include increased salivation, diarrhea, nausea and vomiting, sweating, and bradycardia.
Cholinergic - Edrophonium
Edrophonium is a medication used to help diagnose myasthenia gravis. It helps differentiate myasthenia gravis from a cholinergic crisis, which carries a lot of the same symptoms.
If we give edrophonium to a patient suspected to have myasthenia gravis and they improve, we know that they did have myasthenia gravis.
If we give edrophonium to a patient and they get worse, they are probably having a cholinergic crisis instead. In the case of a cholinergic crisis, your patient will need the antidote, which is atropine (an anticholinergic).
Dopamine agonists for Parkinson's - Levodopa & carbidopa (Sinemet), bromocriptine (Parlodel)
Levodopa and carbidopa (used together) and bromocriptine are dopamine agonists used to treat parkinson's disease. These medications are used to help decrease Parkinson's symptoms including tremors and muscle rigidity.
What is Parkinson's disease?
Parkinson's disease is a Progressive neurodegenerative disease causing muscle rigidity, akinesia (loss of voluntary movement), and involuntary tremor.
Parkinson's disease, including its pathophysiology, signs and symptoms, diagnosis, treatment options, and nursing care are covered in our Med-Surg flashcards.
In Parkinson's disease, patients have too little dopamine and too much acetylcholine. Parkinson's treatment is usually focused on increasing dopamine and decreasing acetylcholine.
Mode of action
Dopamine agonists like levodopa/carbidopa and bromocriptine work by increasing the amount of dopamine in the central nervous system by activating dopamine receptors that regulate motor function and body movement.
Carbidopa and Levodopa drive in their car to the park to increase dopamine in Parkinson’s patients.
Dopamine agonists like levodopa/carbidopa and bromocriptine can cause many side effects, including nausea and vomiting, drowsiness, orthostatic hypotension, dark urine and sweat, possible psychosis, diarrhea, sweating, and bradycardia.
Consuming high protein meals can decrease absorption of levodopa and carbidopa, so patients who are taking these medications should consume a low protein diet to ensure adequate absorption.
Anticholinergic for Parkinson's - Benztropine (Cogentin)
Benztropine is an anticholinergic medication that is used to treat Parkinson's disease by improving symptoms.
Mode of action
Remember that Parkinson's is marked by too much acetylcholine. Benztropine's mode of action is to decrease levels of acetylcholine. This helps to improve symptoms in patients who have Parkinson's disease.
Side effects with benztropine include dry mouth, blurry vision, urinary retention, and constipation. Check out our easy way to remember anticholinergic side effects.
In order to counteract the side effects of these anticholinergics, patients can be advised to chew gum, suck on sugar-free hard candy for dry mouth, wear sunglasses when going outside, and increase their intake of fluids and fiber to counteract constipation.
Okay. In this video, we are going to continue talking about important nervous system medications. If you are following along with cards, I'm on card 82. We'll be talking about medications that are used in Parkinson's, Myasthenia gravis, as well as Alzheimer's disease.
Alright. So let's first talk about a cholinergic agent that is sometimes used in patients who have Alzheimer's. This medication is donepezil.
Donepezil helps to increase acetylcholine by inhibiting the action of cholinesterase, which is an enzyme that breaks down acetylcholine, and it may improve a patient's memory, their cognition, and their ability to perform their activities of daily living, or their ADLs.
Keep in mind that this medication does not cure Alzheimer's disease. It is really just to help improve the patient's memory and cognition, hopefully.
Side effects can include headache, diarrhea, and nausea.
We would administer this medication at night.
And then my little trick for remembering this medication, if you look at the word, donepezil, you have that DON, and then you've got PEZ. So DON't forget things like your PEZ dispenser when you take donepezil.
Alright. Let's now talk about some cholinergic medications that are used to treat Myasthenia gravis. Medications that fall within this class include neostigmine as well as pyridostigmine.
These medications can help improve the strength and mobility in patients who have Myasthenia gravis.
They are also used to help reverse the effects of neuromuscular blocking agents as well.
They work by increasing the amount of acetylcholine at the receptor sites by inhibiting the action of cholinesterase, which is an enzyme that breaks down acetylcholine.
So my weirdo way of remembering these medications is if you look at the two drug names, they both contain Stig. Stig is a famous race car driver in the show Top Gear. So Stig, he's coming in to save the day. He pulls up with his race car, and he's like [braking noise]. And he blocks cholinesterase. And by blocking cholinesterase, he prevents the breakdown of acetylcholine and helps to improve symptoms in myasthenia gravis.
So side effects, as you recall, with anticholinergic medications, you get a lot of drying side effects, right? Can't see, can't pee, can't spit, can't poop, right? With cholinergic medications, everything's going to be very, very moist, so you're going to get side effects such as increased salivation, diarrhea, nausea and vomiting, sweating, as well as bradycardia so just think of all those moist things and that will help you to remember cholinergic side effects.
Another cholinergic medication that's important to know is one called edrophonium.
Edrophonium is used to help diagnose myasthenia gravis and to make sure that's what we're dealing with, myasthenia gravis, as opposed to a cholinergic crisis which has a lot of the same symptoms.
So if we give edrophonium to a patient who we suspect may have myasthenia gravis and they improve, then we know that they did have myasthenia gravis.
If we give edrophonium to a patient and they get worse, then that means they were probably having a cholinergic crisis instead. And then we need to administer the antidote which is atropine, which is an anticholinergic medication.
Alright, now we're going to talk about medications that are used to treat Parkinson's disease. So in Parkinson's disease, patients have too little dopamine and too much acetylcholine. So treatment is usually centered around trying to bring up these dopamine levels and decrease the amount of acetylcholine onboard.
So our first class of medication that we're going to cover are dopamine agonists. Medications that fall within this class include levodopa and carbidopa, which are used together, or bromocriptine.
So these medications are used to help decrease symptoms in Parkinson's disease including tremors and muscle rigidity.
They work by increasing the amount of dopamine in the central nervous system.
There are many, many side effects with these medications. So side effects can include nausea and vomiting, drowsiness, orthostatic hypotension, darkening of urine and sweat, possible psychosis, as well as diarrhea, sweating, and bradycardia.
Keep in mind that consuming high protein meals can actually decrease absorption of levodopa and carbidopa. So patients should actually consume a low protein diet to ensure adequate absorption of this medication.
The way I remember this medication is that carbidopa and levodopa drive in their car to the park (park for Parkinson's disease) to increase levels of dopamine. So both of those words in that -dopa, which will help you to remember that both of those things work together to increase dopamine.
Alright, now let's talk about an anticholinergic medication that is used to treat Parkinson's disease, which is benztropine.
Benztropine helps to bring down those levels of acetylcholine which helps to improve symptoms in patients who have Parkinson's disease.
Because it is an anticholinergic medication, it will have those drying effects. And my mnemonic again for how to remember those anticholinergic side effects is, "can't see, can't pee, can't spit, and can't poop.
So you can expect side effects with benztropine that include dry mouth, blurry vision, urinary retention, and constipation.
So to counteract those anticholinergic side effects, you should advise your patient to chew gum or suck on hard candy for that dry mouth, wear sunglasses when going outside, and then increase their intake of fluids and fiber to help counteract that constipation.
So that's it for this video. We will pick it up with more important nervous system medications in my next video. If you've found value in these videos, be sure to like and subscribe to us here at Level Up RN!
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