Digoxin
Mechanism :
Digoxin is one of the cardiac glycosides, a closely related group of drugs having in common specific effects on the myocardium. Digoxin inhibits sodium-potassium ATPase, an enzyme that regulates the quantity of sodium and potassium inside cells. Inhibition of the enzyme leads to an increase in the intracellular concentration of sodium and thus an increase in the intracellular concentration of calcium. The beneficial effects of digoxin result from direct actions on cardiac muscle, as well as indirect actions on the cardiovascular system mediated by effects on the autonomic nervous system.
Indication :
- Congestive cardiac failure
- Atrial flutter
- Atrial fibrillation
- Supraventricular tachycardia
Contraindications :
Digitalis glycosides are contraindicated in patients with ventricular fibrillation or in patients with a known hypersensitivity to digoxin. A hypersensitivity reaction to other digitalis preparations usually constitutes a contraindication to digoxin.
Dosing :
Maintenance dose should start 12 hours after loading ends.
>10 years:
Use smaller doses in early adolescence and/or in underweight children.
Neonate:
10-30 microgram/kg intravenous loading, followed by 5-10 mcg/kg/day maintenance dose orally.
1 month-2 years:
30 microgram/kg oral loading dose followed by 10-15 mcg/kg/day maintenance dose orally.
2-10 years:
30 microgram/kg oral load then 5-10 mcg/kg/day maintenance dose orally.
10-18 years:
10 microgram/kg oral loading dose followed by 2-5 microgram/kg/day maintenance dose orally.
Adverse Effect :
Anorexia, nausea, vomiting, diarrhea, CNS disturbances, cardiac arrhythmias (sinus bradycardia, conduction disturbances, supraventricular tachyarrhythmia, atrial tachycardia and junctional (nodal) tachycardia), gynaecomastia, skin rashes, weakness, apathy, fatigue, malaise, headache, visual disturbances, depression and psychoses.
Interaction :
Potassium-depleting diuretics: Contributing factor to digitalis toxicity.
Calcium: May produce serious arrhythmias in digitalized patients.
Quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam, and spironolactone: Raise the serum digoxin concentration.
Erythromycin and clarithromycin (and possibly other macrolide antibiotics) and tetracycline: May increase digoxin absorption in patients.
Antacids, kaolin-pectin, sulfasalazine, neomycin, cholestyramine, certain anticancer drugs: May interfere with intestinal digoxin absorption, resulting in unexpectedly low serum concentrations.
Rifampin: May decrease serum digoxin concentration, especially in patients with renal dysfunction, by increasing the non-renal clearance of digoxin.
Thyroid administration: To a digitalized, hypothyroid patient may increase the dose requirement of digoxin.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | 125–250 micrograms per day |
| 10-20 | 125–250 micrograms per day. Monitor levels |
| <10 | Dose commonly 62.5 micrograms alternate days, or 62.5 micrograms daily. Monitor levels |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Not dialysed. Dose as in GFR<10 mL/min |
| CAV/VVHD | Not dialysed. Dose as in GFR=10–20 mL/min |
Hepatic Dose :
No dosage adjustments are recommended.