====== Digoxin (Lanoxin®) ======

<WRAP right 300px>
<WRAP infobox>
^ Drug Overview | {{ :cardio:arrhythmias:digoxin.svg |}}|
| Drug Class | [[cardio:hf:positive_inotropes|Cardiac Glycoside]] |
| Subclass | Na⁺/K⁺ ATPase Inhibitor |
| Primary Uses | [[cardio:heart_failure:start|HFrEF]]; [[cardio:arrhythmias:atrial_fibrillation|Atrial Fibrillation]] |
| Route | Oral / IV |
| Onset (IV) | 5–30 minutes |
| Half-life | ~36–48 hours (normal renal function) |
| Metabolism | Minimal hepatic |
| Elimination | Renal |
| Renal Adjustment | Yes |
| Hepatic Adjustment | No |
| Therapeutic Level | 0.5–0.9 ng/mL (HF) |
| Black Box Warning | No |
</WRAP>
</WRAP>

===== Overview =====

Digoxin is a cardiac glycoside that increases inotropy and enhances vagal tone.

It is used in:

  * [[cardio:heart_failure:start|HFrEF]] (symptom improvement only — no mortality benefit)
  * [[cardio:arrhythmias:atrial_fibrillation|Atrial Fibrillation]] (rate control)

It is NOT first-line therapy in modern heart failure but remains useful in select patients.

<WRAP clear></WRAP>

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===== Mechanism of Action =====

Primary Target:
  * Inhibits Na⁺/K⁺ ATPase pump in cardiac myocytes

Cellular Effect:
  * ↑ intracellular Na⁺
  * ↓ Na⁺/Ca²⁺ exchanger activity
  * ↑ intracellular Ca²⁺

Result:
  * ↑ Contractility (positive inotropy)

Autonomic Effect:
  * ↑ Vagal tone
  * ↓ AV nodal conduction
  * ↑ AV nodal refractory period

Net Effects:
  * Improves systolic function
  * Slows ventricular response in [[cardio:arrhythmias:atrial_fibrillation|AF]]

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===== Indications =====

Cardiovascular:

  * [[cardio:heart_failure:start|HFrEF]] (symptom reduction)
  * [[cardio:arrhythmias:atrial_fibrillation|Atrial Fibrillation]] (rate control)

Not used for:
  * Acute decompensated HF
  * Mortality reduction

See also:
  * [[cardio:hf:positive_inotropes|Positive Inotropes]]
  * [[cardio:arrhythmias:start|Dysrhythmias Module]]

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===== Dosing =====

Heart Failure (maintenance):

  * 0.125–0.25 mg daily

Atrial Fibrillation:

  * Similar dosing
  * Lower doses preferred in elderly

Renal dosing:
  * Reduce dose in CKD
  * Monitor levels carefully

Target serum concentration:
  * 0.5–0.9 ng/mL (HF)
  * Avoid > 2.0 ng/mL

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===== Contraindications =====

Absolute:

  * [[cardio:arrhythmias:ventricular_tachycardia|Ventricular Tachycardia]]
  * [[cardio:arrhythmias:ventricular_fibrillation|Ventricular Fibrillation]]

Relative:

  * [[cardio:arrhythmias:av_block|Advanced AV block]]
  * Severe hypokalemia
  * Severe renal dysfunction

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===== Adverse Effects =====

Common:

  * Nausea
  * Vomiting
  * Anorexia
  * Fatigue

Cardiac:

  * Bradycardia
  * AV block
  * Ventricular arrhythmias

Visual:

  * Yellow vision (xanthopsia)
  * Blurred vision

Toxicity Risk Increases With:

  * Hypokalemia
  * Hypomagnesemia
  * Hypercalcemia
  * Renal dysfunction

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===== Digoxin Toxicity =====

Mechanism:

  * Excess intracellular calcium
  * Increased automaticity
  * Delayed afterdepolarizations

ECG Findings:

  * Scooped ST segments (“dig effect”)
  * AV block
  * Ventricular ectopy

Treatment:

  * Correct electrolytes
  * Stop drug
  * [[cardio:arrhythmias:digoxin_immune_fab|Digoxin Immune Fab]]

See:
  * [[cardio:arrhythmias:bradycardia|Bradycardia Algorithm]]

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===== Drug Interactions =====

Increase Digoxin Levels:

  * [[cardio:arrhythmias:amiodarone|Amiodarone]]
  * [[cardio:ccb:non_dhp|Non-DHP Calcium Channel Blockers]]
  * Macrolides
  * Verapamil

Electrolyte-mediated Risk:

  * [[cardio:diuretics:loop:start|Loop Diuretics]] → hypokalemia
  * [[cardio:diuretics:thiazide:start|Thiazides]] → hypokalemia

Additive AV Nodal Suppression:

  * [[cardio:beta_blockers:start|Beta-Blockers]]
  * [[cardio:ccb:non_dhp|Non-DHP CCBs]]

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===== Monitoring =====

  * Serum digoxin level
  * Renal function
  * Potassium
  * ECG

Monitor especially in:

  * Elderly
  * CKD
  * Patients on interacting drugs

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===== Comparison Within Heart Failure Therapy =====

Unlike:

  * [[cardio:raas:acei|ACE Inhibitors]]
  * [[cardio:raas:arb|ARBs]]
  * [[cardio:hf:spironolactone|MRAs]]
  * [[endocrine:sglt2:start|SGLT2 Inhibitors]]

Digoxin:

  * Does NOT reduce mortality
  * Improves symptoms only
  * Useful in HFrEF with AF

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===== Clinical Pearls =====

  * Narrow therapeutic window.
  * Renally cleared — dose carefully.
  * Hypokalemia dramatically increases toxicity risk.
  * Yellow vision is classic but uncommon.
  * Think of digoxin when AF + HFrEF coexist.

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===== Related =====

  * [[cardio:heart_failure:start|Heart Failure]]
  * [[cardio:hf:positive_inotropes|Positive Inotropes]]
  * [[cardio:arrhythmias:start|Dysrhythmias]]
  * [[cardio:arrhythmias:digoxin_immune_fab|Digoxin Immune Fab]]
  * [[cardio:intro:start|Cardiovascular Pharmacology]]