6.7 Cardiac Glycosides
Digoxin
Digoxin is a cardiac glycoside medication that has been used for centuries to treat heart failure. It has three effects on heart muscle: positive inotropic action (increases contractility, stroke volume and, thus, cardiac output), negative chronotropic action (decreases heart rate), and negative dromotropic action (decreases conduction of cardiac cells).[1]
Mechanism of Action: Digoxin works by inhibiting the sodium and potassium pump, which results in an increase in intracellular sodium and an influx of calcium into cardiac cells, causing the cardiac muscle fibers to contract more efficiently and increase cardiac output.[2]
Indications: This medication is used as second-line treatment for clients who have heart failure or atrial fibrillation. Due to the risk for digoxin toxicity, the clinical use of digoxin has decreased and alternative, safer medications are being used.
Nursing Considerations: Apical pulse should be taken for a full minute before administration of this medication. If the apical pulse is less than 60, the dose should be withheld, and the prescribing provider notified.
Serum digoxin levels should be monitored, with a normal therapeutic range from 0.8 to 2 ng/mL.
Serum potassium levels should also be closely monitored for clients on digoxin because hypokalemia increases the effect of digoxin and can result in digoxin toxicity. Normal potassium level is 3.5 to 5.0 mEq/L, and a result less than 3.5 should be immediately reported to the provider.
Nurses should closely monitor for signs of digoxin toxicity. Geriatric clients have an increased risk for developing digoxin toxicity. Digibind is used to treat digoxin toxicity.
Side Effects/Adverse Effects: Overdose or accumulation of digoxin causes digoxin toxicity. Signs and symptoms of digoxin toxicity are bradycardia (heart rate less than 60), nausea, vomiting, visual changes (halos), and arrhythmias. Cardiotoxicity is a serious adverse effect with ventricular dysrhythmias. Toxicity of this medication typically occurs at greater than 2 ng/mL, but some clients may have signs and symptoms at lower levels. Pediatric clients typically present with bradycardia or arrhythmias if toxicity is occurring.
Decreased renal function, hypokalemia, hypercalcemia, and hypomagnesemia may increase risk for digoxin toxicity.
Common side effects include GI symptoms, headache, weakness, dizziness, anxiety, depression, delirium, and hallucination.[3]
Health Teaching & Health Promotion The client should be instructed to follow the prescribed dosing regimen and take medications at the same time each day. The client should be cautious not to double up on medication doses. Additionally, the client should consult the health care provider if two or more doses of medication are missed for follow-up instruction.
Clients should receive health teaching regarding pulse rate monitoring and report any pulse rate less than 60. If the client experiences signs of digoxin toxicity, this should be reported to the provider immediately. The medication should be stored in its original container, and care should be taken not to mix the medication with other medications.[4]
Now let’s take a closer look at the medication grid for digoxin in Table 6.7a.[5]
Table 6.7a Digoxin Medication Grid
| Class/Subclass | Prototype/Generic | Nursing Considerations | Therapeutic Effects | Side/Adverse Effects |
|---|---|---|---|---|
| Cardiac Glycoside | digoxin | Assess apical heart rate
Assess serum digoxin and potassium levels Assess for signs and symptoms of digoxin toxicity |
Increased cardiac output | Digoxin toxicity; early signs include nausea, vomiting, and diarrhea
Bradycardia and arrhythmias Headache, weakness, dizziness, and mental changes such as anxiety or hallucinations Gynecomastia (with prolonged use) |
Critical Thinking Activities 6.7
- Why should a nurse assess the apical pulse for 1 full minute before administering digoxin?
- How does a nurse evaluate if digoxin is effective?
- Why must the nurse monitor serum potassium levels, as well as digoxin levels?
- A nurse enters a client’s room, and the client complains “My vision seems strange, and I feel nauseated.” What is the nurse’s next best action?
Note: Answers to the Critical Thinking activities can be found in the “Answer Key” sections at the end of the book.
Digoxin Immune Fab (DigiFab)
Digoxin immune fab (DigiFab) is used to treat life-threatening digoxin toxicity.
Mechanism of Action: DigiFab binds to digoxin molecules, reducing free digoxin.
Indications: This medication is the antidote for life-threatening digoxin toxicity.
Nursing Considerations: There are no contraindications when using DigiFab.
Side Effects/Adverse Effects: The most common effects a client may experience are to have worsening heart failure, hypokalemia, and worsening atrial fibrillation.
Health Teaching & Health Promotion: Clients should report any signs of worsening heart failure or hypokalemia immediately to the health care provider.
Now let’s take a closer look at the medication grid for DigiFab in Table 6.7b.[6]
Table 6.7b Medication Grid for DigiFab
| Class/Subclass | Prototype/Generic | Nursing Considerations | Therapeutic Effects | Side/Adverse Effects |
|---|---|---|---|---|
| Antidote | digoxin immune fab (DigiFab) | Administer when clients are experiencing life-threatening digoxin toxicity | Reduce free digoxin | Worsening heart failure
Worsening atrial fibrillation Hypokalemia |
- McCuistion, L., Vuljoin-DiMaggio, K., Winton, M., & Yeager, J. (2018). Pharmacology: A patient-centered nursing process approach. pp. 443-454. Elsevier. ↵
- McCuistion, L., Vuljoin-DiMaggio, K., Winton, M., & Yeager, J. (2018). Pharmacology: A patient-centered nursing process approach. pp. 443-454. Elsevier. ↵
- This work is a derivative of DailyMed by U.S. National Library of Medicine in the Public Domain. ↵
- uCentral from Unbound Medicine. https://www.unboundmedicine.com/ucentral ↵
- This work is a derivative of DailyMed by U.S. National Library of Medicine in the Public Domain. ↵
- This work is a derivative of DailyMed by U.S. National Library of Medicine in the Public Domain. ↵
