CC Pharm | Digoxin

Lanoxin (Digoxin) 80/20 Clinical Summary 1. Expected Action & Mechanism Positive Inotrope: Inhibits the Na+/K+-ATPase pump1, raising intracellular sodium. This reverses sodium-calcium exchange to increase intracellular calcium, boosting myocardial contractility, force, and velocity12. Negative Chrono/Dromotrope: Increases vagal activity, slowing AV nodal conduction and prolonging refractory period to slow ventricular rate3. 2. Therapeutic Use & Selection Indicated for heart failure (HF) and controlling ventricular rate in chronic atrial fibrillation (AF)4. Off-label for fetal supraventricular tachyarrhythmias5. Benefit: Boosts cardiac output, lowers sympathetic tone/heart rate, and causes diuresis2. Beta-blockers, verapamil, and diltiazem are replacing it for AF rate control13. Does not convert acute AF to sinus3. 3. Crucial Administration Protocols IV: Preferred (IM causes severe pain)67. Dilute 1 mL in $\ge$4 mL sterile water, 0.9% NaCl, or D5W to prevent precipitation8. Inject slowly over $\ge$5 minutes to avoid sudden vasoconstriction8. Oral (PO): Tablet bioavailability is 60–80% (solution 70–85%)910. High-fiber meals decrease absorption910. 4. Dosing & Renal Safety Guidance Dosing must be based on lean body weight (LBW), efficacy, and serum levels4. Geriatric: PIM (avoid first-line); if used, limit to 125 mcg/day to reduce toxicity risk1112. Renal GFR Adjustments (Half-life 36–48h)13: >50 mL/min: No adjustment14. 10–50 mL/min: Give 25%–75% of dose every 36h14. <10 mL/min: Give 10%–25% of dose every 48h14. Dialysis: Not removed by dialysis15. 5. Adverse Reactions & Toxicity Severe Risks: AV block, bradycardia, VT/VF, cardiac arrest, hyperkalemia, bowel ischemia/necrosis1617. Toxicity Signs: Blurred/yellow vision (xanthopsia), GI distress (nausea, vomiting, anorexia), and CNS changes (confusion, delirium, hallucinations)16more_horiz. 6. Priority Nursing Pearls (The 20% to Know) Monitoring: Track heart rate (bradycardia risk)16, toxicity, and clinical efficacy4. Labs: Monitor GFR/CrCl, potassium (hypokalemia is an adverse reaction; hyperkalemia occurs in toxicity), and digoxin levels16more_horiz. Interactions: Digoxin is a P-gp substrate; P-gp inhibitors/inducers trigger drug interactions13. WPW use increases ventricular response risk4.