11.10 Angiotensin Receptor Blockers

Angiotensin II Receptor Blockers or we can say, ARBs. Now, in this presentation, we gonna talk in which disease process we use these ARBs for, what is the mechanism of action, and we gonna relate and understand depending on the mechanism of action why we use this medication in particular disease process. Then, we gonna go over the side effects and nursing consideration, contraindication, and then finally we will go over how do we find out which drugs is ARBs or how do we easily recognize this drug is ARBs.

So, let’s find, first start with the indication. These drugs are mainly used in heart failure, to treat the high blood pressure, they are used in Diabetes Mellitus, but not to treat the Diabetes. It is used to prevent the kidney damage in Diabetes patient. And also in some cases, it’s shown to help with Diabetic neuropathy as well. And it is also used instead of ACE inhibitor due to their side effects. Because one of the main side effects of ACE inhibitor has is the dry cough. And sometimes, it’s so persistent, it’s not tolerable by the patient, that they have to switch to the ARBs. So, one of the reasons we use these ARBs medications as well.

So, let’s talk about the mechanism of action. So, before looking into the ARBs, you should have looked at the RAA system and how it works in our body. And, if you have looked at that one, here we have Angiotensin II, that’s gonna work in our body in these different ways, and it’s gonna produce the effects. Like, it’s gonna increase the sympathetic system, it’s gonna increase the sodium and water reabsorption, excretion of potassium and so forth. Now, this Angiotensin II Receptor Blockers blocks the receptors of this Angiotensin II. So, whenever we have this Angiotensin in our blood, it’s not gonna able to bind to those receptor and produce these effects which is gonna do the totally opposite of those effects. So, let’s talk about those effects when these ARBs medication blocks the receptor, it doesn’t let Angiotensin II produce its effect.

Okay. We’ll talk into the second slide. So, let’s say, you’re blocking this, Angiotensin II by ARBs. So, one of the Angiotensin II effect is it increases sympathetic nervous system. Now, when it increases the sympathetic nervous system, it gonna cause the vasoconstriction when we block this, it’s not gonna really increase the sympathetic nervous system, it’s gonna decrease in sympathetic nervous system, it’s gonna decrease the vasoconstriction, which is gonna decrease blood pressure. That is the one reason we use this medication, to treat the high blood pressure. Second, in normal RAA system, Angiotensin II receptor increases the sodium and water reabsorption. When we block, it’s gonna decrease the sodium and water reabsorption and it’s gonna increase potassium reabsorption. Or, some people may say, it’s gonna decrease the sodium excretion, same thing. So, when it decreases the sodium and water reabsorption, it’s gonna decrease the blood volume, which is eventually gonna decrease in blood pressure, and cardiac workload. When we decrease the cardiac workload, we can use this medication in the heart failure. This is the one reason we use this medication for the heart failure. Now, this, at the same time, also increases the potassium reabsorption. When it increases the potassium reabsorption, it can increase the potassium level in our body. We need to keep this in mind and this will help us to understand what are the side effects of this medication is gonna have. Now, it also gonna decrease the ADH secretion from pituitary gland. Now, when it decreases the ADH secretion, which is anti-diuretic hormone, it’s gonna increase water excretion in kidneys. And when it increases the water excretion, it’s gonna decrease the blood volume. And we can refer back that it’s gonna do what? Decrease in the blood pressure and cardiac workload. So, there are many different ways, it decreases the blood pressure and cardiac workload, that’s why we are using this medication to treat the high blood pressure. And also, it’s helpful in heart failure as well. So, since we understood the mechanism of action, and why you use this medication in heart failure and high blood pressure, let’s go over the side effects and what are the nursing considerations as a nurse we have to look for and also educate the patient about.

Alright. So, obviously, the first side effects, it’s gonna be the hypotension. So, this medication can decrease the blood pressure significantly because remember, Angiotensin II is a potent vasoconstrictor, and when you block the effect of Angiotensin II, it’s gonna cause vaso, it’s gonna prevent vasoconstriction and it’s gonna decrease the blood pressure significantly. So, what are the symptoms you see if a patient is hypotensive? Dizziness, lightheadedness, faintness upon rising. So, you want to look for these symptoms when you give especially the first dose of the medication. You want to assess the blood pressure before giving the first dose and monitor after, regularly, in order to make sure the patient doesn’t get really hypotensive. Because if they get hypotensive, and if they try to get up, due to the dizziness and faintness, they can fall. That’s the one of the precaution and teaching we have to do as a nurses to patient.

Now, let’s go back to this previous slide really quickly and look at this potassium reabsorption, okay? And we talked about, it can increase the potassium level. So, that’s why one of the side effect, it’s gonna increase, it can cause a high potassium level in our body. So, what are the symptoms for high potassium level? Confusion, numbness or tingling in hands, feet, cardiac arrhythmia. So, we have to look for those symptoms and have to teach to the patient about those signs and symptoms, as well. Now, since it can increase the potassium level in our body, it is contraindicated in the potassium sparing diuretic and salt substitute because the potassium sparing diuretics gonna increase the potassium level as well. And, salt substitute contains potassium. So, that’s why you don’t really wanna give too much medication or any kind of substitute or any kind of supplement with this medication which is gonna increase the potassium as well. So, if you give it, the potassium can go up really, to a lethal level. Like a normal potassium level, if you say, 3.5 - 5.2. It can be different from different hospitals, sine they all use different instruments and everything. So, but, normally it would go above this 5.2.

Now, since this medication gonna prevent the blood flow to the kidney by decreasing the blood pressure, by decreasing the blood volume, you want to really monitor the BUN and Creatinine in order to assess kidney function and you wanna do these labs periodically so we can monitor kidney function all the time. And obviously, this medication is contraindicated in liver damage because most of the medication get metabolized by the liver and if the liver is damaged, this medication can accumulate to the toxic level and can cause more side effects. And also, for the renal disease as well.

Now, how do you find out which drugs is/are ARBs? Let’s go over some examples. Losartan, Valsartan. So, if you see this medication, at the very end, all drugs ends with -sartan. So, any drug that ends with a -sartan is ARBs which is Angiotensin II Receptor Blockers. So, drugs that end with -sartan, ARBs.

Alright, this is all about the ARBs. If you have any questions, you can e-mail us or contact us. Thanks for watching.