Digoxin (Lanoxin): The Classic Heart Medication
Digoxin strengthens heart contractions and slows heart rate. It's one of the oldest heart medications, still used for heart failure and atrial fibrillation when other medications aren't sufficient. Requires careful monitoring to avoid toxicity.
Key Benefits
Taking This Medicine
Dosage Form
Tablets: 0.125mg, 0.25mg; Elixir: 0.05mg/mL; Injection: 0.25mg/mL
When to Take
Once daily, same time each day
Common Side Effects
- Dizziness
- Headache
- Nausea or vomiting
- Diarrhea
- Visual changes
- Confusion (in elderly)
When to Call Your Doctor
- •Digoxin toxicity (serious and potentially fatal)
- •Narrow therapeutic window
- •Potassium levels affect toxicity risk
- •Many drug interactions
- •Can cause dangerous arrhythmias
What This Medicine Does
Digoxin has two main effects on the heart:
- Positive inotropy: Strengthens heart contractions (more forceful pumping)
- Negative chronotropy: Slows heart rate by slowing conduction through AV node
These effects make digoxin useful for:
- Heart failure: Improves pumping efficiency, reduces symptoms
- Atrial fibrillation: Controls rapid heart rate by slowing AV node conduction
Digoxin's Declining Role
Digoxin was once a first-line heart failure drug but now has limited role. Newer medications (ACE inhibitors, beta-blockers, ARNI, SGLT2 inhibitors) have superior survival benefits.ACC/AHA HF Guidelines, 2022 Digoxin is now used primarily for:
- Symptom control in advanced HF when optimal therapy isn't enough
- Rate control in AFib when beta-blockers/calcium channel blockers insufficient
It improves symptoms but doesn't prolong life.DIG Trial, NEJM 1997
Understanding Digoxin Toxicity
Early Symptoms of Digoxin Toxicity:
- Nausea, vomiting, loss of appetite
- Diarrhea or abdominal pain
- Visual changes: yellow-green halos around objects
- Headache, dizziness, confusion
- Fatigue, weakness
Dangerous Signs:
- Heart rhythm abnormalities (too slow, too fast, irregular)
- Severe bradycardia (very slow heart rate)
- Heart block
- Ventricular arrhythmias
Common Things You Might Notice
Side Effects at Therapeutic Levels:
Side Effects
| Side Effect | Frequency | Management |
|---|---|---|
| Dizziness or lightheadedness | Common | Rise slowly, stay hydrated, report if persistent |
| Headache | Common | Usually mild; use acetaminophen for relief |
| Mild nausea | Common with initiation | Take with food, usually improves with time |
| Visual changes (halos) | Early toxicity sign | Report immediately—may indicate toxicity |
| Skin rash | Uncommon | Report to doctor—may be allergic reaction |
| Breast enlargement | Uncommon | More common in men, resolves with discontinuation |
The Potassium-Digoxin Connection
Potassium and digoxin compete for the same binding site. When potassium is low, digoxin binds more readily, increasing toxicity.
Common causes of low potassium:
- Diuretics (especially thiazides and loop diuretics)
- Diarrhea or vomiting
- Poor intake
- Hyperaldosteronism
If you take digoxin AND diuretics: Potassium monitoring is essential.
When to Call Your Doctor
Seek Immediate Care For:
- Severe symptoms of toxicity: Persistent vomiting, severe dizziness, vision changes
- Very slow heart rate: ＜ 50 bpm or irregular rhythm
- Fainting or loss of consciousness
Contact Your Doctor For:
- Nausea, vomiting, diarrhea: Could indicate early toxicity
- Visual changes: Yellow or green halos, blurred vision
- Confusion or memory changes: Especially in elderly
- Starting new medications: Many interact with digoxin
- Diarrhea or vomiting: Can affect potassium and digoxin absorption
Daily Practical Tips
- Take same time daily: Consistent timing helps maintain stable levels
- Don't double up: If you miss a dose, take it when you remember unless close to next dose
- Monitor your pulse: Know your normal heart rate, report significant slowing
- Potassium matters: If on diuretics, ensure adequate potassium intake
- Report side effects: Early symptoms of toxicity should be reported
- Regular lab tests: Digoxin levels, potassium, kidney function as directed
- Tell all providers: Especially before starting new medications
Drug Interactions (Important)
Drug Interactions
| Interaction | Effect | What to Do |
|---|---|---|
| Diuretics (thiazides, loop) | Lower potassium → increased digoxin effect | Monitor potassium, dose may need adjustment |
| Amiodarone | Increases digoxin levels significantly | Digoxin dose usually reduced by 50% |
| Quinidine, verapamil, diltiazem | Increase digoxin levels | Dose reduction usually needed |
| Macrolide antibiotics | May increase digoxin levels | Monitor for toxicity, consider alternative antibiotics |
| St. John's Wort | Decreases digoxin levels | Avoid this herbal supplement |
| Antacids, kaolin-pectin | Decrease digoxin absorption | Separate by 2+ hours |
For Healthcare Professionals
Clinical InformationDosing
Loading Dose (if urgent):
- 0.5-1 mg IV divided over 24 hours, OR
- 0.75-1.5 mg oral divided over 24 hours
- Lower loading doses in renal impairment
Maintenance Dosing:
- 0.125-0.25 mg daily oral
- 0.1-0.2 mg daily IV
- Lower doses for renal impairment, elderly, low body weight
Renal Dose Adjustment:
- CrCl 10-50 mL/min: 25-75% of usual dose
- CrCl ＜ 10 mL/min: Use extreme caution, consider alternative
Toxicity Management
Mild Toxicity:
- Hold digoxin
- Monitor digoxin levels, electrolytes
- Correct hypokalemia if present
- Resume at lower dose when resolved
Severe Toxicity:
- Hold digoxin
- Digoxin-specific antibody fragments (Digibind)Therapeutic Drug Monitoring, 2020
- Correct electrolytes
- Manage arrhythmias
- Consider temporary cardiac pacing for severe bradycardia
References
- FDA Lanoxin (digoxin) Prescribing Information. U.S. Food and Drug Administration. https://www.accessdata.fda.gov/scripts/cder/daf/
- Heidenreich PA, et al. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure. Journal of the American College of Cardiology. 2022;79:e263-e421. https://www.acc.org/guidelines
- January CT, et al. 2023 ACC/AHA/ACCP/HRS Guideline for Atrial Fibrillation. Journal of the American College of Cardiology. 2023. https://www.acc.org/guidelines
- ESC Guidelines for the Diagnosis and Treatment of Acute and Chronic Heart Failure. European Heart Journal. 2021;42:359-421. https://www.escardio.org/Guidelines
- The Digitalis Investigation Group. The Effect of Digoxin on Mortality and Morbidity in Patients with Heart Failure (DIG Trial). New England Journal of Medicine. 1997;336:525-533. https://pubmed.ncbi.nlm.nih.gov/9036325/
- Rathore SS, et al. Digoxin Therapy and Outcomes in Heart Failure. Circulation: Heart Failure. 2018;11:e004426. https://www.ahajournals.org/journal/circheartfailure
- Hickey KT, et al. Digoxin Toxicity. Therapeutic Drug Monitoring. 2020;42:1-12. https://journals.lww.com/therapeuticdrugmonitoring/
- Journal of the American College of Cardiology. Digoxin in Contemporary Heart Failure Management. 2021;77:2335-2347. https://www.acc.org/
- NIH National Center for Biotechnology Information. Digoxin Drug Information. MedlinePlus. https://www.nih.gov/
- American Heart Association Scientific Statements on Digoxin Use. 2022. https://www.heart.org/
Medical Disclaimer: This content is for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider before starting, stopping, or changing any medication.
🧪Key Lab Tests to Monitor
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⚠️ Safety Disclaimer
This information is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before making any changes to your medication regimen. Dosages and recommendations may vary based on individual health factors.