Pharmacology, part 5: Cardiovascular Medications - Hypertension & the RAAS system
by Cathy Parkes April 30, 2020 Updated: April 14, 2022 9 min read
In this article, we cover some cardiovascular medications for hypertension and the RAAS system. The Pharmacology Nursing 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 are thinking critically about side effects on your exams, something that may be helpful to remember is that for all drugs prescribed for hypertension, HYPOtension is always a possible side effect if the medication is doing its job too well.
RAAS system review
The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system within the body that regulates blood pressure and fluid balance. Check out our Med-Surg A&P review within the endocrine system playlist to learn more about the RAAS system. The RAAS system’s job is primarily to prevent HYPOtension by increasing blood pressure. These are the main components of the RAAS system, that the medications in this article block or inhibit:
- Angiotensin-converting enzyme (ACE)
- Angiotensin II
Direct renin inhibitor - aliskiren
An important medication used to treat hypertension is a direct renin inhibitor called aliskiren, which goes by the brand name Tekturna.
Mode of action
Aliskiren acts by inhibiting renin, which is at the top of the RAAS system, and prevents angiotensinogen from being activated into angiotensin I. Basically, it pumps the brakes on the RAAS process which prevents the RAAS system from raising blood pressure like it’s intended to.
Aliskiren looks like Alice and Karen. Alice and Karen gang up to stop Angie (angiotensinogen).
Side effects of aliskiren include hypotension as well as angioedema (sudden, short-term skin swelling) and GI upset.
Black box warning
Aliskiren carries a black box warning because of fetal toxicity. Drugs that act directly on the RAAS system can cause injury to a developing fetus. This is because these drugs reduce renal function in the fetus which can lead to birth defects.
As with most blood pressure medications, it’s important to monitor the patient's blood pressure during aliskiren therapy.
ACE inhibitors - captopril, lisinopril
ACE inhibitors can be used for hypertension as well as heart failure, a myocardial infarction, and diabetic nephropathy. Common ACE inhibitors include captopril (Capoten) and lisinopril (Prinivil, Zestril).
You get a thrill when you pull an ACE...ACE inhibitors end in -pril!
Mode of action
Remember that Angiotensin-converting enzyme (ACE), which is from the lungs, converts angiotensin I into angiotensin II. It’s a step in the RAAS system, and that pesky RAAS system is working to increase blood pressure! So, ACE inhibitors block the conversion of angiotensin I into angiotensin II, which results in vasodilation and decreases blood pressure.
The key side effect, as with most hypertension medications, is hypotension. If your medication is working too well, hypotension will be the result. Other important side effects include angioedema, cough and elevated potassium (hyperkalemia).
Black box warning
ACE inhibitors are also toxic for fetuses! Again, ACE is part of the RAAS system, and drugs that act on the RAAS system are not good for fetuses.
Nursing care and patient teaching
As with all hypertension meds, monitor the patient’s blood pressure during therapy. Teach your patient to change positions slowly, because of the resulting orthostatic hypotension, which is a form of low blood pressure that happens when you stand up suddenly.
If you see orthostatic and forget what it means, you can break it down into ortho- (straight/upright) and -static (still or stop) to decode this term. Check out our Medical Terminology flashcards to help you break down unfamiliar any medical term you come across! Knowing medical terminology word parts (roots, prefixes, suffixes) can be a tremendous help on exams.
Patients with orthostatic hypotension can sit up slowly and start by dangling their feet off the bed before standing. This will give their blood pressure a chance to catch up to the next move they want to make!
Angiotensin II Receptor Blockers - losartan, valsartan
Angiotensin II receptor blockers are used to control high blood pressure, heart failure and diabetic nephropathy (kidney disease) in people with diabetes. Common medications that fall within this class include losartan (Cozaar) and valsartan (Diovan).
Mode of Action
Remember that angiotensin II is part of the RAAS system, which schemes all day long to raise your blood pressure. Angiotensin II receptor blockers prevent angiotensin II from being able to trigger vasoconstriction, so you actually get vasodilation. Open up those blood vessels, and you lower blood pressure!
Key side effects of losartan and valsartan include hypotension, dizziness and GI upset. The dizziness is usually caused by the hypotension.
Sartan looks like Satan. Seeing Satan would likely make your blood pressure drop, make you dizzy, and make your stomach hurt.
Black box warning
Angiotensin II receptor blockers are also toxic for fetuses! Again, angiotensin II is part of the RAAS system, and drugs that act on the RAAS system are not good for fetuses.
Nursing care and patient teaching
Like the other hypertension medications mentioned before, when a patient is on an angiotensin II receptor blocker like losartan and valsartan, you will need to monitor their blood pressure and instruct them to get up slowly so they don’t have a severe blood pressure drop and fall down!
Aldosterone Antagonist - eplerenone
Aldosterone antagonists are used for hypertension as well as heart failure after a heart attack. The most common medication in this class to be familiar with is eplerenone, which goes by the brand name Inspra.
Mode of Action
Aldosterone antagonists block the effects of aldosterone. Remember that in the RAAS system, angiotensin II causes the mineralocorticoid aldosterone to be released. And Aldosterone works to raise your blood pressure by causing reabsorption of sodium and water.
Aldosterone antagonists actually block mineralocorticoid receptors, which inhibits the effect of aldosterone, resulting in increased sodium excretion and decreased body fluid, which lowers blood pressure.
Eplerenone does an epic job of blocking aldosterone.
A key side effect with eplerenone is hyperkalemia (high potassium levels). Patients can also experience dizziness as a result of hypotension when they are on eplerenone.
Potassium & hyperkalemia
To think critically about hyperkalemia as a side effect of eplerenone, remember that aldosterone causes renal excretion of potassium. If aldosterone is blocked, then we’re not excreting as much potassium as we could be, and it can build up.
The normal range for potassium is 3.5 - 5.0 mEq/L. Potassium above 5 mEq/L indicates hyperkalemia. In addition to being a medication side effect, hyperkalemia can be caused by diabetic ketoacidosis (DKA), metabolic acidosis, salt substitutes (because they are made with potassium chloride instead of sodium chloride), and kidney failure.
This lab value and many more are covered in our Lab Values flashcards for easy reference.
When a patient is taking an aldosterone agonist, you will need to monitor their blood pressure and potassium levels.
The Pharmacology Video Series is intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI and NCLEX.
Starting in this video, we are going to be talking about cardiovascular medications. There are a lot to know in this category, but we're going to break it off into chunks to help make it more manageable. If you are following along with cards, I'm on card 11 [in the Pharmacology Flashcards], and we're going to start off with medications that are used for hypertension or angina.
So before we get into our first batch of medications, let's do a review of the renin-angiotensin-aldosterone system or RAAS system.
So renin is released by the kidneys in response to a decrease in renal blood flow or low blood pressure.
Then, renin activates angiotensinogen into angiotensin I.
Then, ACE, which is angiotensin converting enzyme, converts angiotensin I into angiotensin II.
And then, angiotensin II does a number of things.
The first thing it does is it causes vasoconstriction of the blood vessels.
It also causes water and sodium to be reabsorbed at the kidneys.
And then, finally, it causes the release of aldosterone from the adrenal cortex, which, in turn, also causes reabsorption of water and sodium at the kidneys so these medications that I'm about to go over, they will act on different parts of this renin-angiotensin-aldosterone system.
So the first medication we're going to talk about that is used to treat hypertension is a direct renin inhibitor, and the medication that's important to know in this class is aliskiren, and it's used to treat hypertension.
It acts by inhibiting renin, which is at the top of our RAAS system, which prevents angiotensinogen from being activated into angiotensin I.
So the way I remember this medication-- if you look at the word aliskiren, it kind of looks like Alice and Karen. So Alice and Karen gang up on Angie, right, so Angie being angiotensinogen, to stop it.
So side effects with aliskiren include hypotension as well as angioedema and GI upset.
This medication also carries a black box warning because of fetal toxicity.
It's going to be really important to monitor the patient's blood pressure during therapy.
And, again, like I shared in my introduction video to this whole series, for a lot of these medications, you could kind of figure out what one of the key side effects is going to be just by its mode of action. This medication is used to treat hypertension, so if it does its job too well, we're going to end up with hypotension, which is a side effect for this medication.
Now, let's talk about ACE inhibitors. ACE inhibitors include medications such as captopril and lisinopril.
They will all end in that -pril, which kind of looks like thrill, so if you're playing cards and you draw an ace, then you get a thrill. So that kind of helps you to remember that medications that end in that -pril are ACE inhibitors.
So ACE inhibitors can be used for hypertension as well as heart failure, a myocardial infarction, and diabetic nephropathy.
They work by blocking the conversion of angiotensin I into angiotensin II, which results in vasodilation.
They do have some key side effects. So hypotension is going to be a key side effect. Again, if our medication is doing its job too well-- it's being used for hypertension. If it works too well, we're going to end up with hypotension. So hypotension is a key side effect.
Other really important side effects to know include angioedema, cough, and elevated potassium.
So those all start with A, C, E. So A for angioedema, C for cough, and E for elevated potassium. And so that's how you can remember those key side effects in addition to hypotension.
Other side effects. This drug is toxic for fetuses, so it does carry a black box warning, and you would not want to use this during pregnancy.
And then it's important to monitor blood pressure during therapy, and you want to teach your patient to change positions slowly because of that hypotension side effect. So when a patient has hypotension, and if they get up too quickly, they may be going right back down. So you want them to kind of sit up on the side of the bed and dangle their feet for a little while before just popping out of bed. So hopefully, that's helpful.
Now, let's talk about angiotensin II receptor blockers. So medications that fall within this class include losartan and valsartan.
These medications will all end in that -sartan, which kind of looks like Satan, and if you saw Satan, it would probably make your blood pressure drop, make you feel dizzy, and make your stomach hurt, which are key side effects with this class of medication.
So angiotensin II blockers are used to treat hypertension as well as diabetic nephropathy.
They work by blocking the effects of angiotensin II which results in vasodilation.
So key side effects, you can probably guess what one of them's going to be. It's hypotension. In addition, it's dizziness and GI upset.
It also carries a black box warning because of fetal toxicity.
And again, when your patient is on this medication, you're going to want to monitor their blood pressure carefully. And also, teach them to change their positions slowly because of that hypotension.
Okay. So the last medication that works within that RAAS system is an aldosterone antagonist. So the medication in this class that I would be familiar with is eplerenone.
And it is used for hypertension as well as heart failure after an MI.
It works by blocking mineral corticoid receptors which inhibits the effect of aldosterone and results in reabsorption of sodium and water.
So the way I remember this medication is that eplerenone does an epic job of blocking aldosterone. So the E-P at the beginning of eplerenone kind of reminds me of epic. And again, the end of it is that -one. So eplerenone does an epic job of blocking aldosterone.
Side effects include hyperkalemia, very important side effect to know with this medication, as well as dizziness.
So when a patient is taking this medication, you want to make sure you're monitoring their blood pressure during therapy. But also monitoring their potassium levels because of that side effect of hyperkalemia.
In my next video, we're going to talk about more medications that are used to treat hypertension. If you found this video helpful, be sure to like, leave your comment, and share a link with your classmates or friends in nursing school!
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