11.12 Calcium Channel Blockers

Calcium Channel Blocker (CCBs). So, in this module, we gonna learn about the mechanism of action, what are the indication, side effects, and how do you recognize these calcium channel blockers. So, mechanism of action. So, before we understand the mechanism of action, let’s talk about the calcium channels. Calcium Channels. So, where do you find this calcium channel in our body? First one, you find in SA node, in heart, you find in AV node, cardiac myocytes; which is basically the heart cell, and vascular smooth muscles. Now, SA node, as we know, is a pace maker. So, what is the function of calcium channel in this SA node, AV node, cardiac myocytes, and vascular smooth muscles? So, they all have a calcium channel. When this channel opens, let’s say here’s a calcium channel. Calcium channel. And this is a, this is a wall. Let’s say this is a cell, either one of these, could be SA node, AV node, cardiac myocyte or vascular smooth muscles, could be either one. This is a cell. This is calcium channel. When this channel opens, all the calcium moves in. Calcium enters the cell. When the calcium enters the cell, it causes the contraction and a, contraction, let’s say, if you’re talking about the cardiac myocytes, cardiac heart cells, heart cells or vascular smooth muscles, it causes the contraction of those muscles and if you’re talking about the SA node and AV node, it causes the production of electrical activity. So, it produce impulse. So, that’s the function of calcium. And, I mean, there’s so much in detail about the mechanism of action, how does the calcium enters, helps in the phosphorylation of the protein of these heart muscles and vascular smooth muscles. So, as a nurse, we don’t really need to know in that detail. However, we need to know, like when the calcium enters into the cell, it causes the contraction and also produces the impulse. So, calcium channel blocks these channels. When it blocks, it doesn’t allow this calcium enter these cells. And when it doesn’t allow calcium to enter the cell, it prevents contraction, so, it will cause vasodilation, it will not let SA node and AV node produces the impulse. So, if the heart is beating at 90 beats/minute, it’s gonna be beating at lower rate. So, it decreases heart rate, it decreases conduction velocity. Now, if you remember learning about the heart, especially the AV node, AV node is responsible for lowing the electrical impulse in the heart. And when we block the calcium channel in AV node, it’s gonna even slow down the impulse more. So, it’s gonna decreases the conduction velocity in the heart. And it also gonna decrease the force of contraction in heart. So, these are the effects when we block calcium channel in cardiac cell, SA node, AV node, and vascular smooth muscles. That it prevents the contraction, so it causes the vasodilation, decreases the heart rate, decreases the conduction velocity and decrease force of contraction in heart. So, that’s the mechanism of action and the effects of, effects by blocking the calcium channel in our body. So, since we understood this mechanism of action, let’s see in which disease condition we can use this medication for.

So, absolutely for the hypertension. We can use this medication because this medication causes vasodilation in vascular smooth muscles. Now, we use this medication for angina. So, what happen, how we can use this medication? What is the main purpose that we can use these medications for angina? So, it decreases the blood pressure, absolutely it causes the vasodilation, so, decreased blood pressure which is systemic vascular resistance. Now, when there is a decrease in systemic vascular resistance, ventricles can easily pump the blood out of the heart because it doesn’t have to overcome the high blood pressure. Now, the blood pressure is low, it can just pump blood really easily without so much effort into those dilated vessels. So, it decreases the ventricular workload. Right? By decreasing the blood pressure. And also, you can say in the other terms that it decreases the afterload which is basically the systemic vascular resistance. Because if the blood pressure is high, the afterload is gonna be high, which means, if the blood pressure is high, the ventricle will have to contract really, give it really force and use a lot of energy to overcome that blood pressure and pump blood out of the ventricles. While the blood pressure is low, the ventricles won’t have to create that much energy to pump the blood out of the ventricles. So, the ventricle afterload is gonna be decreased. When the ventricle afterload decreases, basically the heart workload gonna decrease and heart muscle won’t need that much oxygen in order to pump the blood out of the heart. So, will decrease the amount of oxygen for heart cells. And that will decrease the angina. Okay. And also, since this medication blocks the calcium channels in our body, especially the heart, helpful in preventing the cardiac arrhythmia as well. Alright, so, these are the main 3 indication we use this medication for, hypertension, angina and cardiac arrhythmia.

So, what are the side effects of this medication? Obviously, the severe hypotension since it causes the vasodilation. It can cause a significant bradycardia, because as we talked, that it also affects the SA node that it decreases the production of the electrical activity in SA node gonna decrease the heart rate. So, it can cause the bradycardia, headache and flushing and also sometime it can cause a reflex tachycardia. Now, this is kinda confusing why it causes the bradycardia and sometimes it causes the reflex tachycardia. So, here’s an explanation. So, this is our, let’s say this is our aortic arch. In aotic arch, there’s some special cells located right there. It’s called the Baro receptor. Now, the baro receptors has a nerve endings, right? Like that, that sends the signals to the brain. So, this is our brain, let’s say. Brain. Now, what does the Baro receptor detects? Baro receptor detects change in blood pressure. So, if the blood pressure is high, the walls gonna stretch a little bit more. And if the blood pressure is low, the arteriole’s walls not gonna stretch that much. So, what does this baro receptor detects is the increase and the decrease in the blood pressure and sends signals to the brain. When there’s a decrease in blood pressure, it sends a signal to the brain and say hey, we have a decrease in blood pressure, we’re not getting enough blood, we need, the heart needs to pump faster in order to supply more blood. So, if there is a decrease in blood pressure, heart rate will go up. Brain will increase the heart rate. When the blood pressure is high, the brain is gonna say, Baro receptor gonna say, hey, we have a too much blood pressure. We have too much blood. We don’t really need that much. So, it gonna send a signal to the brain and the brain will say, okay, we’ll decrease the heart rate. So, you won’t get that much blood you don’t need. So, it’s gonna decreases the heart rate. Now, what does this calcium channel blocker does, if the calcium channel blocker decreases the blood pressure, and when it decreases the blood pressure, it’s gonna increases the heart rate by this baro receptor reflex. Okay? That’s how it causes the reflex tachycardia.

What are the contraindication and precaution with this medication? You can’t really give the digoxin because digoxin actually decreases the heart rate as well. So, that’s why you don’t wanna really give this medication or be cautious when you’re giving with the digoxin ‘cause it can significantly decreases the heart rate. Beta blockers for the same reason, that it decreases the heart rate. Antihypertension medications such as ACE inhibitors, ARBs, some other medication like, you can say, alpha blockers, some diuretics can also decrease the blood pressure. So, any kind of hypertensive medication, you wanna be cautious that it doesn’t decrease the blood pressure really significantly. Now, since this medication blocks the calcium channels, prevents the normal function of calcium. But if we give too much calcium? Well it’s gonna just nullify the effect of this medication. So, if you’re giving a IV calcium to patient and if they are on calcium channel blocker, these calcium channel blockers not gonna work. So, this IV calcium prevents the effect of this calcium channel blocker. And also, this is thing to remember for NCLEX and for exam as well, is a Grape fruit juice. Grape fruit juice significantly interacts with many of the medications. It either decreases or increases their effect. So, if you have a question, if you’re not sure, usually the grape fruit juice because you don’t really wanna give grapefruit juice with any medications. Just to be like extra cautious. Okay, so grapefruit juice interacts with these medications as well.

Now, how do you find out a calcium channel blocker? And, as we talked in the first slide that it works on the heart and also works on the vessels. Now, there’s a way to remember which medication works on the heart, which medication works on the vessels and which medication works on both. Now, if you see on the right side, these Amlodipine, Nicardipine, Nifedipine, Nimodipine, Felodipine. All the medication has -dipine. So, any medication in the calcium channel blockers that ends with the dipine works only on vessels. This is kinda the trick to remember, that this medication that ends with the dipine, it’s gonna work only on the vessels. That means, it’s gonna decreases the blood pressure, however, it’s not gonna decrease, the heart rate is not gonna decrease the force of contraction or whatever the effects this medication has on the heart because this one works only only on vessels. Now, if you see this example on the left side, Diltiazem and Verapamil, their names are different than other calcium channel blockers, like they don’t end with dipine. So, this one works on the heart and works on the vessels. So, that’s kinda little trick to remember. Their name are different from other medication in the same class and they works on the heart and vessels, both. While the other, these drugs work only on the vessels. And especially, just kinda interesting thing to know or to remember this Nimodipine, it can cross blood brain barrier. So, blood brain barrier also called as BBB. And that is the reason we can use only this medication to prevent vasospasm in the brain. You can’t really give any other calcium channel blocker to prevent the vasospasm in the brain because they are not able to cross the blood brain barrier. This is the only medication, Nimodipine, can cross the blood brain barrier and it can prevent the vasospasm. This is the mostly used medication on neuro ICU because they have a like a aneurysm, they get the aneurysm fixed and after, there’s a high chance that they’ll have a vasospasm and they need to be on this medication for at least 21 days in order to prevent any incidence of vasospasms.

Okay. So, that was it about the calcium channel blocker. If you have any questions or any concerns, you can e-mail us or contact us. Thanks for watching.