Pharmacology, part 8: Cardiovascular Medications - Glycosides & Antidysrhythmic Classes I & II
by Cathy Parkes October 27, 2020 Updated: December 29, 2021 7 min read
In this article, we cover cardiovascular medications - Glycosides and Antidysrhythmic classes I & II. 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.
Cardiac glycosides: Digoxin
Digoxin is a cardiac glycoside used to treat heart failure and to slow the heart rate in patients with atrial fibrillation and atrial flutter.
Mode of action
Digoxin provides a positive inotropic effect, so it helps the heart to increase the force and efficiency of its contractions. It also has a negative chronotropic effect, which results in a decreased heart rate. Remember that inotropic has to do with strength, and chronotropic refers to heart rate (think of a clock).
When you dig a hole, dig SLOW and DEEP.
Because digoxin slows the heart rate, its side effects include bradycardia. Another important side effect to know about is digoxin toxicity. You will need to monitor your patient carefully for signs of digoxin toxicity, including GI upset, such as vomiting, sudden fatigue, weakness, and vision issues.
Before administering digoxin, take your patient’s apical pulse for one full minute. If their pulse is under 60 beats per minute, you will want to hold off on giving them this medication.
Remember that digoxin should never be used in a patient with a junctional dysrhythmia. In fact, digoxin toxicity can lead to junctional dysrhythmias.
The patient’s digoxin level will need to be monitored during therapy, and you may need to treat for digoxin toxicity and bradycardia.
Digoxin range & digoxin toxicity
The therapeutic serum levels of digoxin should be somewhere between 0.5 and 2 ng/mL. Digoxin levels over 2.0 ng/dL can indicate digoxin toxicity. The signs and symptoms of digoxin toxicity include GI upset, vision issues, and fatigue.
Hypokalemia (low potassium) can place the patient at higher risk for digoxin toxicity. Monitor your patient’s potassium levels during digoxin therapy to ensure they stay in the right range.
Digoxin toxicity can be treated with digoxin immune FAB (Digibind), which is basically the antidote for Digoxin.
Digoxin and potassium are some of the many lab value ranges covered in our Lab Values flashcards. If you need an easy way to memorize these ranges for your Pharm or Med-Surg classes, check them out!
If a patient has bradycardia as a side effect of taking digoxin, it can be treated with atropine, which is an anticholinergic medication we cover next in this series.
Class I antidysrhythmics (sodium channel blockers): Procainamide, lidocaine
Class I antidysrhythmics are sodium channel blockers and are used for things such as ventricular dysrhythmias as well as supraventricular tachycardia. Medications that fall within this class include procainamide and lidocaine (Xylocaine). Notice these medications both have "cain."
Our EKG Series covers these dysrhythmias, and you might find it a helpful reference when learning about antidysrhythmics.
NOTE: Lidocaine is also used as a topical analgesic.
Procainamide and lidocaine can cause some pretty serious side effects including hypotension, dysrhythmias, lupus (chronic inflammatory disorder of the connective tissue), leukopenia (low white blood cells), and thrombocytopenia (decreased platelet count).
The latter three side effects are all covered in the Immune System section of our Med-Surg Series and Med-Surg flashcards because they are disorders and complications you need to know about for that course, so if you’re taking that course, we highly recommend them!
Black box warning
Procainamide and lidocaine also come with a black box warning. If a patient uses procainamide for a prolonged amount of time, they may test positive for ANA, which is the antinuclear antibody, which basically means they are having an autoimmune response due to the medication.
During therapy with procainamide or lidocaine, monitor the patient's EKG; vital signs; and complete blood count (CBC) levels, which measure for white and red blood cells, hemoglobin, hematocrit, and platelets. You will also monitor your patient’s blood levels for procainamide. Therapeutic blood levels of procainamide are typically between 4 and 8 µg/mL.
Class II antidysrhythmics (beta-blockers): Propranolol, metoprolol, atenolol
Class II antidysrhythmics are beta-blockers and include medications such as propranolol, metoprolol, and atenolol. We covered these medications when we explained hypertension and angina medications, but they can also be used for dysrhythmias such as atrial fibrillation, atrial flutter, and ventricular dysrhythmias.
You can learn more about atrial fibrillation, atrial flutter, and ventricular fibrillation using our EKG Flashcards.
Common side effects with beta-blockers like propranolol, metoprolol, and atenolol include hypotension, bradycardia, fatigue, weakness, and erectile dysfunction. It’s very important to remember that nonselective beta-blockers like propranolol can result in bronchospasm, so we would never want to give it to someone who has asthma because of this side effect of bronchospasm.
Beta-1 vs nonselective beta-blockers
Beta-1 blockers block beta-1 receptors on the heart, while nonselective beta blockers are not selective between the heart vs. the lungs, so they block beta-1 receptors in the heart and beta-2 receptors in the lungs.
You can easily remember the difference between these two types of beta-blockers by remembering these two Cool Chicken hints from Cathy:
To remember that Metoprolol and Atenolol are cardioselective (beta 1), remember that you only have 1 (birth) ma.
Please Listen Carefully - these beta blockers (Propanolol, Labetalol, Carvedilol) are NON-selective. They will impact the lungs too!
In this video, we are going to start going over antidysrhythmic medications. We're going to discuss cardiac glycosides, and we will also cover Class I and II antidysrhythmic medications.
Let's talk about cardiac glycosides. If you are following along with cards, I am on card number 21 [of the Pharmacology Flashcards]. And if you look at the back of the card, there's a lot of stuff that is in bold and red, which means that these things are really important to know.
Digoxin is the medication that we're going to talk about here. It is a cardiac glycoside. It is used for heart failure. It is also used for atrial fibrillation as well as atrial flutter.
Its mode of action is that it provides a positive inotropic effect, so it helps the heart to increase the force and efficiency of the contractions. It also has a negative chronotropic effect, which results in decreased heart rate.
So side effects of this medication include dysrhythmias, such as bradycardia, and also digoxin toxicity is definitely a risk with this medication. And you're going to want to monitor your patient carefully for signs of digoxin toxicity.
So these signs can include GI upset, such as vomiting, sudden fatigue or weakness as well as well as vision issues. So if your patient is taking digoxin and is reporting some of these symptoms, then you need to suspect that they may have digoxin toxicity.
So before you administer digoxin, you're definitely going to need to take your patient's pulse. And if their pulse is under 60 beats per minute, you are going to hold the digoxin. You are not going to give it to them.
You're also going to want to monitor their digoxin levels during therapy. So the therapeutic range should be somewhere between 0.5 and 2. And keep in mind that hypokalemia can place the patient at higher risk for digoxin toxicity. So you're going to want to make sure their potassium levels stay in the right range so they don't end up with this toxicity.
And then if they have bradycardia, we can treat that with Atropine which is an anticholinergic medication, and then you would treat digoxin toxicity with digoxin immune fab or Digibind.
So the silly tip or trick I have for this one is when you dig a hole, you want to dig slow and deep. So that kind of reminds you that digoxin helps those contractions slow down and become more forceful just like if you were digging a hole slow and deep. Hopefully, that's helpful for you.
Now, let's talk about Class I antidysrhythmics. So we'll cover Class I and II in this video, and then we'll cover Class 3, 4, and 5 in my next video. So Class I are sodium channel blockers. And medications that fall within this class include procainamide and lidocaine. So both of these medications contain the word "cain."
So these medications are used for things such as ventricular dysrhythmias as well as supraventricular tachycardia.
They do cause some pretty serious side effects. So side effects associated with Class 1 antidysrhythmics include hypotension, dysrhythmias, lupus, leukopenia, thrombocytopenia, as well as a black box warning because if a patient uses procainamide for a prolonged amount of time, they may test positive for ANA, which is the antinuclear antibody, which basically means they are having this autoimmune response because of this medication, so very serious side effects.
So during therapy, you're going to want to monitor the patient's EKG, their vital signs, their CBC levels. We're also going to want to monitor their blood levels of procainamide. So therapeutic blood levels are typically between 4 and 8.
Now let's cover Class II antidysrhythmics, which are beta blockers and include medications such as propranolol, metoprolol, and atenolol. So we did already talk about these medications when we covered hypertension and angina medications, but they can also be used for dysrhythmias such as atrial fibrillation, atrial flutter, and ventricular dysrhythmias.
So common side effects with these beta blockers include hypotension, bradycardia, fatigue, weakness, and erectile dysfunction.
Also, if we are talking about a nonselective beta blocker such as propranolol, it can also result in bronchospasm. So if you recall, we would never want to give a nonselective beta blocker to someone who has asthma because of this side effect of bronchospasm.
And just to review the differences between beta-1 and nonselective beta blockers, with beta-1 blockers, you have one ma - right? - or mother. So that helps you to remember that metoprolol and atenolol are your beta-1 blockers.
And then for nonselective beta blockers, remember my mnemonic, "please listen carefully," right? Propranolol, labetalol, and carvedilol affect beta-1 and beta-2 receptors in the lungs, which is why you get that bronchoconstriction with nonselective beta blockers.
So again, you wouldn't give those to a patient with asthma, versus beta-1 blockers, those are going to be more safe for someone who may be suffering from asthma.
Okay. In my next video, we will go through the rest of the antidysrhythmic medications. If these free videos are helping you, then definitely be sure to like this video and share a link with your classmates and friends in nursing school!
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