Feb 16, 2023
ABCD Antihypertensive Mnemonics ACEIs ARBs Beta and Calcium Channel Blockers Diuretics
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Hypertension treatments are really about a few drug classes: ACEIs and ARBs, Beta Blockers, Calcium Channel Blockers, Diuretics, and a few more. This episode has a few mnemonics and a focus on prefixes and suffixes that will help you remember them.
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Welcome to the Memorizing Pharmacology podcast. I'm Tony Guerra, a pharmacist and author of the Memorizing Pharmacology book series, bringing you mnemonics, cases, and advice for succeeding in Pharmacology. Sign up for the email list at memorizingfarm.com to get your free suffixes cheat sheet or find our mobile-friendly self-paced online pharmacology review course at residency.teachable.com/p/mobile.
Let's get started with the show. I'm going to go over anti-hypertensives in a way that hopefully makes a bit of sense. It's actually easier to compare them side by side with a bunch of these and I'll get into that, but let's start with what the ABCD of hypertension really is. Okay, so it's just talking about the drug classes: ACE, ARBs, the Alpha One blockers, the beta blockers, calcium channel blockers, and diuretics. Let's start with A, B, C, and D and there's going to be some oddball ones that I'll talk about at the end.
The alpha agonists like clonidine, methyl dopa, the dilators that will peripheral vasodilators hydralazine nitropresside and then the direct reading inhibitor Alice Kirin but these are going to be the kind of heart and soul of our anti-hypertensive therapy and what you'll notice is that stems go really well with these. So when I say stems I mean the endings these in these cases they are all suffixes but for Angiotensin converting enzyme Inhibitors it's pril as in lisinopril.
Angiotensin II receptor blockers it's sartan. The Alpha One blocker is as a sin be careful I've seen zosin a lot it's azosin but again that'll get you there too which is a little bit different than tamsulosin we'll talk about the differences in a minute. Beta blockers again be careful first and second Generations have the same stem of olol and that third generation will have something that kind of indicates there is an alpha blocking component uh the alol with labetalol or the dilol for dilation with Carvedilol.
Calcium channel blockers we divide them into dihydropyridines like nifedipine or non-dihydropyridines which are diltiazem and Verapamil. Then the diuretics really furosemide is not for hypertension in general really it's Hydrochlorothiazide that's first line and then the potassium sparing diuretics but Hydrochlorothiazide is definitely preferred.
So when we talk about being able to recognize them that's kind of the first thing you want to be able to do is make sure that as you look at these endings you can recognize all these but what we'll do is we'll kind of cut it down so that makes a little bit easier. I know this seems a little bit busy but soon enough you'll be able to get all of these.
Okay alright well let's just look at what first line is first line are the Angiotensin converting enzyme Inhibitors like lisinopril and the ARBs like losartan. Calcium channel blockers like nifedipine, diltiazem, Verapamil though calcium channel blockers are first line in African Americans because of poor outcomes with ACE inhibitors. Then diuretics Hydrochlorothiazide is certainly first line.
So let's take a look at the renin Angiotensin aldosterone system some people call it renin or the RAS system. The big thing is recognizing what happens here in this pathway and we'll put three of the drugs in here so lisinopril that works here at ACE where Angiotensin one cannot become Angiotensin II if you block this enzyme why does that matter well Angiotensin II is a potent vasoconstrictor and it also acts to release aldosterone which would normally hold on to salt and water so if you block Angiotensin II you vasodilate instead of vasoconstrict and you don't stimulate these release of aldosterone so you're not holding on to salt and water okay increasing blood pressure so the ultimate thing that happens is that you decrease blood pressure okay.
And this happens with lisinopril by blocking this enzyme here or with Losartan which is an Angiotensin II receptor blocker I'm actually blocking the enzyme itself okay or The receptors on the enzyme and then Alice Kiran that blocks renin directly right at the beginning but for whatever reason the outcomes were not what we wanted so this is definitely not a first line drug but the first thing is recognize the medications by their stems recognize they have different mechanisms of action within the RAS system and then we'll combine them to look at them side by side so what I do is I take the one that has something more and put it on the left and I have something that has something less and put it on the right.
So, with the ACEs and ARBs, when we go through our eye match mnemonic, we see that I have similar indications: hypertension, congestive heart failure, MI. But when we get to the adverse effects, we see that really the taste, some irritation of the throat, the cough, that's really Angiotensin converting enzyme inhibitors, not really so much Angiotensin II receptor blockers. So when you get there, you're like okay well let me cross that one off on the right and so I'm just remembering one set of things and then one difference. And we'll see that this happens over and over again with our ABCD.
So Angiotensin converting enzyme inhibitors, that's the one that causes that taste, the throat, the cough and it sure it causes angioedema, it causes hyperkalemia. But we switch to an ARB because it doesn't have that issue with taste, the irritation of the throat, the cough and those things. So understanding how those work side by side is critical.
Okay when you look at contraindications which you would think if you have other potassium sparing medications like spironolactone diuretic or pregnancy certainly a contraindication as well that's out. And then really it's just letting the patient know hey you know if you get this dry cough don't try to treat it let us know we can give you something that won't cause that and then maybe talking about the foods and other things that might add to the hyperkalemia.
Alpha blockers we talked about before and we'll just kind of go through the three parts of it where in the beginning we talked about the stem, the azosin stem of prazosin doxazosin terazosin all very similar. And we used the prazosin mnemonic using the word prazosin to remind ourselves of the three indications: prazosin - the pr for prostate or BPH; raz to remind us is for Raynaud's which is when your fingers are really cold or your toes are really cold because just not enough blood getting to them; and then hypertension. And we looked at the last s-i-n for that and it does this by relaxing the bladder neck for prostate and by causing vasodilation for Raynaud's and hypertension.
But the adverse effects come from that vasodilation so I have a picture here of somebody who's kind of a little bit shaky that's getting that maybe first dose effect where first time they took it they didn't realize they were supposed to take it right before bed so they don't fall down. I really feel that reflex tachycardia or orthostatic hypotension or first dose syncope or first dose phenomenon but again big mechanism of action here is that vasodilation.
Okay and then you put them side by side and you see that prazosin is actually second line for hypertension because of that adverse effect that they might just drop so we don't want to give something like that so BPH right now it's hypertension those are certainly indications but when you look over on the other side and take something like tamsulosin or alfuzosin that are really only for BPH it's first line for that condition because it's really not going to cause that kind of first dose syncope phenomenon hypotension all that stuff to the same extent.
So what we do is we take the mechanism and we say okay we're going to have the same Alpha One bladder smooth muscle and vasodilation of blood vessels and maybe we darken out that vasodilation of blood vessels to make clear that we're really being a lot more selective okay in both cases. The elderly is a concern coronary artery disease certainly and then we want our patients to be slow to get from sitting to standing okay.
Beta blocker stems we talked about how the first generation affects beta 1 beta 2 again you have one heart so it affects the heart reduces heart rate but also it affects the lungs it may cause some degree of bronchoconstriction. And so Propranolol is a concern with asthmatic but with the second generation it was beta one specific and we have our bam mnemonic where bisoprolol Atenolol metoprolol these are three of those drugs that are in the second generation.
And then third generation was our Carvedilol and our labetalol which are also non-selective but not in the same way as Propranolol because they also have Alpha One activity so that allows for vasodilation okay because what the body is going to do is as soon as it sees heart rates going down it's gonna try to vasoconstrict because it wants to get heart rate back or blood pressure back up. And so Alpha One blocking takes care of that by causing vasodilation again. The dil or dial is in that stem so when you compare them side by side first versus second you see very similar in terms of what they do.
Hypertension, migraine, and China atrial fibrillation again, beta blockers are an antiarrhythmic. Okay, but again the mechanism is that we block beta 1 and beta 2 receptors so our adverse effect with beta 1 would be bradycardia. Our adverse effect with beta 2 would be bronchoconstriction. Okay, and so we take that bronchoconstriction one and beta 2 away when we get to the second generation. Now again we can cause bradycardia, heart block have are bradycardia, heart block are certainly contraindications but also asthma with first generation not so with second generation. And then they all really do mask those signs and symptoms of hypoglycemia so we want to be careful with our diabetics.
Get to the calcium channel blockers, the C in our ABCD mnemonic here we really need to separate the dihydropyridines from the non-dihydropyridine. So the non-dihydropyridines affect both vasodilation and the heart so diltiazem which is Cardizem and Verapamil which is Calan versus dihydropyridine which is dilation only so the dipine the dilation only the nifedipine or Procardia XL all these D's try to use that to remember that this is just affecting the artery it is not affecting the heart as an antiarrhythmic.
Okay, and so when you put them side by side you would put the non-dihydropyridines here and what you want to do is show that okay hypertension angina they're both good for that but these two are good for atrial fib because it does affect the heart nifedipine is not they both block calcium channels in the smooth muscle but still diltiazem of rap milk are going to have decreased contractility and heart rate both will cause hypotension peripheral edema and constipation but here bradycardia is the issue and here reflex tachycardia is the issue.
So again that vasodilation, the body's not happy with that and it's going to cause the heart sometimes to increase the heart rate which may seem counterintuitive. Again watching out for the elderly and grapefruit juice can be an issue with both of these.
Okay, we talked about diuretics going from left to right uh you know figure out what goes where but with hypertension we're going to take some of them away. We're going to take the PCT ones away because those are for emergency conditions and then we're going to kind of focus on first the thiazides which are first line and then talk a little bit about Loop potassium sparing which are second line.
Okay so first line you just cross everything else off really. The distal convoluted tubule with the thiazides especially Hydrochlorothiazide that's our really first line for hypertension and we'll probably combine this with triamterene as the form of Dyazide.
"So, we have the hypo and hyperkalemia kind of balancing itself out, but that’s first line. Then we sure can take a look at maybe the potassium sparing diuretics: spironolactone, amiloride, triamterene, eplerenone. But really those and the loop diuretics (furosemide, torsemide, bumetanide) are definitely not first line for hypertension. Okay, alright. So Hydrochlorothiazide again, not only for hypertension but also edema. It blocks that sodium and water reabsorption in the distal convoluted tubule. We’re worried about hypokalemia with Hydrochlorothiazide and also that hyperuricemia if gout is an issue. Watching again for that sulfa allergy and then just making sure that the electrolytes, the labs are all on the up and up for the patient.
Generally, we might pair certain diuretics with other potassium sparing diuretics to make sure that we don’t have that hypo or hyperkalemic effect. But note that when you do block aldosterone especially with spironolactone, you do have that issue with gynecomastia. Certainly if you’re going to have that maybe you’re going to have decreased libido. Those types of things come along with giving something like spironolactone when you’re going to block that aldosterone hormone. Okay, but again we’re talking about diuretics really that Hydrochlorothiazide is going to be our preferred medication.
There are some oddballs and usually it’s just here’s a thing or two to remember about each one. The alpha agonist clonidine, we talked about how that really suppresses that norepinephrine outflow so you get that reduction in blood pressure but that can be terribly sedating and causes tremendous fatigue. Methyldopa is one of the ones that we can consider with pregnancy in certain situations.
The peripheral vasodilators so hydralazine again maybe for an emergency or with pregnancy and then Nitroprusside is another dilator but a really strange toxicity to have that cyanide toxicity going along with it.
And then the renin inhibitor aliskiren, that’s the one where we’re really worried about where we’re in the RAS system and it’s the area where the ACE inhibitors are and the Angiotensin II receptor blockers. This aliskiren works at the very beginning and just blocking renin altogether but we’ve just found that that’s really just not the way to go in practice.
Again this is just informational purposes only if you’ve got a medical condition consult a medical professional. Thanks for listening to the Memorizing Pharmacology podcast. You can find episodes, cheat sheets and more at memorizingpharm.com. Again you can sign up for the email list at memorizingpharm.com to get your free suffixes cheat sheet or find our mobile friendly self-paced online pharmacology review course at residency.teachable.com/P/mobile. Thanks again for listening.
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