Pharmacology, part 8: Cardiovascular Medications - Glycosides & Antidysrhythmic Classes I & II

by Cathy Parkes

In this video

Cardiac glycosides: Digoxin

  • What is Digoxin used for?
  • Mode of action
  • Digoxin side effects
  • Administration
  • What to monitor
  • How to treat bradycardia
  • How to treat digoxin toxicity
  • Trick for remembering digoxin

Class I antidysrhythmics (sodium channel blockers): Procainamide, lidocaine

  • Side effects
  • Black box warning
  • What to monitor

Class II antidysrhythmics (beta blockers): Propranolol, metoprolol, atenolol

  • Side effects
  • How to remember differences between beta-1 and nonselective beta blockers

Full transcript

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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