Pharmacology, part 7: Cardiovascular Medications - Vasodilators and Antianginals
by Cathy Parkes October 26, 2020 Updated: December 29, 2021 6 min read
In this article, we cover vasodilators and antianginal cardiovascular medications. 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.
Vasodilators are medications that open blood vessels, and nitroprusside (brand name Nitropress) is a vasodilator used in heart failure or a hypertensive crisis. A hypertensive crisis is a severe increase in blood pressure that can lead to a stroke.
Mode of action
Nitroprusside is a vasodilator that works by relaxing the muscles in your arteries and veins to help them dilate or widen. This brings blood pressure down very quickly and allows blood to flow more easily by reducing both preload and afterload, which are the beginning and end stages of the heart pumping. It can also be used to keep blood pressure low during surgery.
Nitroprusside carries a black box warning because the severe drop in blood pressure that it causes can be dangerous.
With nitroprusside, there are a few key side effects that are unique and that you don’t see very often in other medications: cyanide toxicity and thiocyanate (cyanide + thiosulfate) toxicity. These are somewhat rare, but do happen. The cyanide ion shows up when the body metabolizes nitroprusside.
Patients can also experience dizziness as well as GI upset.
Nitroprusside might "pruss" (press) you into the ground when your BP rapidly decreases.
If your patient is taking nitroprusside and experiences extreme hypotension as a result, you will need to take some interventions based on your facility policy. This can include raising the patient's legs, decreasing the dose of nitroprusside, and increasing fluids.
To assess for the potential of cyanide toxicity, monitor serum cyanide levels.
This medication must be protected from UV light, so an opaque brown bag should be placed over the IV bag.
Antianginals: nitroglycerin, isosorbide mononitrate, isosorbide dinitrate
The important medications you should be familiar with in the antianginal class include nitroglycerin as well as isosorbide mononitrate (brand name Imdur) and isosorbide dinitrate.
Mode of action
Nitroglycerin, isosorbide mononitrate, and isosorbide dinitrate work to treat angina through vasodilation. They decrease the preload of the heart, and they also decrease myocardial oxygen demand (the amount of oxygen the heart needs).
The side effects of antianginal medications nitroglycerin, isosorbide mononitrate, and isosorbide dinitrate can include headaches, reflex tachycardia (increased heart rate in response to decreased blood pressure) and orthostatic hypotension.
If you eat some "icy sorbet" it might give you a headache (brain freeze) just like isosorbide medications
It is vitally important to educate patients that they can NOT take this medication within 24 hours of having taken erectile dysfunction meds (such as sildenafil or tadalafil), as these are also potent vasodilators. When taken in combination, the patient could experience a dangerous or even fatal level of hypotension.
If a patient prescribed sublingual (under-the-tongue) nitroglycerin is at home, they will need to keep that medication stored in a cool, dark place.
If they have chest pain, they can take up to three tablets of their nitroglycerin, but no more.
Instruct your patient that if they are experiencing chest pain, they should first sit/lie down, then place one nitroglycerin tablet under the tongue, then wait five minutes. If they are still having chest pain, they need to call 911 and put a second tablet under the tongue, waiting another five minutes, then if there's still no relief, they can take a third, but no more than three total.
If you are giving nitroglycerin topically (transdermally/on the skin), make sure you wear gloves or you could absorb some of the medication! You are likely already wearing gloves, but this is something to be aware of since gloves do break.
Transdermal nitroglycerin is often applied on the patient’s chest. When you apply a new dose, make sure to remove the prior dose. Rotate sites, and choose a clean, hairless area to place the new dose. Applying nitroglycerin to the hair doesn’t work!
In this video, we are going to talk about some important vasodilators. If you are following along with cards, I am on card number 19 [in the Pharmacology Flashcards], which talks about nitroprusside, which is a vasodilator that is used for a hypertensive crisis.
The mode of action of this medication is that it causes direct vasodilation of arteries and veins, so it brings that blood pressure down very quickly. It reduces both preload and after load. So this medication, like I said, it brings the blood pressure down very rapidly, so hypotension is going to be a very important side effect for you to know.
In fact, this particular medication does carry a black box warning because it causes a dangerous drop in blood pressure. So that's definitely a key side effect.
A couple of other key side effects to keep in mind are cyanide toxicity as well thiocyanate toxicity. So those aren't side effects that you see every day. And in fact, I don't know another medication that has those. So those are unique side effects that I would remember with nitroprusside.
Other side effects can include dizziness as well as GI upset.
So we have one of our level of crew members who provided a great tip for remembering this drug. So nitroprusside may "pruss" you into the ground (or press you into the ground) when your blood pressure rapidly decreases.
So if your patient is getting nitroprusside and gets "prussed" into the ground, then has severe hypotension, then you'll want to take some interventions based on your facility policy. This can include raising the patient's legs, decreasing the dose of nitroprusside, and increasing fluids. But again, you'll need to refer to your facility policy for those interventions.
Now let's talk about medications that are used to treat angina. The important medications that I would be familiar with include nitroglycerin as well as isosorbide mononitrate and isosorbide dinitrate.
So these medications work to treat angina through vasodilation. So they decrease the preload, and they also decrease myocardial oxygen demand.
The side effects of these antianginal medications are very important to know. They include orthostatic hypotension as well as a headache and possible reflex tachycardia.
So the way that I remember these isosorbide medications cause a headache, is I think about eating some icy sorbet, which kind of looks like isosorbide. And when you eat an icy sorbet, it might give you a headache because it's so cold. And that helps me to remember that isosorbide medications also can give you a headache as a side effect.
So, if your patient has sublingual nitroglycerin, then they need to keep this stored in a cool dark place. If they have chest pain, they can take up to three tablets, right? So they would place one under the tongue, wait five minutes. If they are still having chest pain, they need to call 911, and then put a second one under the tongue, wait five minutes, and then if there's still no relief, they can take a third, but no more than three.
And then, if you are giving nitroglycerin topically, you want to make sure you're wearing gloves so that you're not absorbing the medication in your hands.
And just in general, wear your gloves as soon as you walk in the patient's room. It's just best practice.
And then, you want to remove the prior dose. So often, we apply this nitroglycerin on the patient's chest. So you want to make sure you remove the prior dose. You want to make sure you're rotating sites and you want to choose a clean, hairless area to place the new dose. Right? So if the patient has a bunch of hair and you stick it on top of the hair, it's not going to get absorbed. So you want to make sure you choose a hairless area.
In my next video, we will get into antidysrhythmic medications. If our free videos have helped you, be sure to like this video and subscribe to us here at Level Up RN!
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