Digoxin
Common Brand Names: Lanoxin
Therapeutic Class: Class IV antiarrhythmic
Common Injectable Dosage Forms:
Injection: 0.1 mg/mL pediatric injection and 0.25 mg/mL in ampules and syringes
Dosage Ranges:
For full digitalization in adults with normal renal function, loading doses of 8-12 mcg/kg are usually administered by giving 50% of the total dose as the first dose, then 25% at 4 hours, and another 25% at 8 hours. Maintenance doses are based on therapeutic response and can be estimated by the following formula: daily % loss = 14 + CrCl( (mL/min)/5
Pediatric and neonatal digitalization doses generally range from 15-50 mcg/kg based on age, with maintenance doses generally 20-35% of loading dose.
Therapeutic Drug Level: Between 0.5 and 2 nanograms/mL
Administration and Stability: IM administration of digoxin is not generally done due to severe local reactions at injection sites and unpredictable absorption and should be given slowly over a period of at least 5 minutes or diluted 4-fold with a compatible solution (sterile water, NS) and given over the same period. Stable for 48 hours at room temperature and refrigerated in concentrations of 250 mcg/100 mL with D5W or NS. pH 6.8-7.2
Pharmacology/Pharmacokinetics: While the exact mechanism of digoxin has not been fully elucidated, it is thought the main activity is related to direct action on the force and velocity of myocardial systolic contractions. This increases cardiac output and reflexively reduces heart rate and causes diuresis in edematous patients. It also decreases conduction velocity through the AV node. Digoxin is widely distributed in body tissues, with 20-30% being serum protein bound. It is excreted in the urine primarily as unchanged drug, with an average elimination half-life of 34-44 hours.
Drug and Lab Interactions: DIURETICS which cause electrolyte disturbances may also produce glycoside toxicity. Concomitant IV administration with calcium supplements may cause arrhythmias. QUINIDINE, FLECAINIDE, and AMIODARONE may increase serum digoxin levels and lead to toxicity. Other drugs leading to increased digoxin levels include verapamil and indomethacin. Concomitant use with sympathomimetics may increase risk of arrhythmias.
Contraindications/Precautions: Digoxin is contraindicated in patients with ventricular fibrillation. The drug should be used with caution in many patients with certain types of arrhythmias, as the cardiac glycosides may be arrhythmogenic. Use with caution when IV is given to hypertensive patients, as it may cause transient elevations in blood pressure. Pregnancy Category C.
Monitoring Parameters: Digoxin serum concentrations, heart rate and rhythm, serum potassium, magnesium, and calcium, renal function, noncardiac signs of toxicity (confusion, depression).
Adverse Effects: The main risk of adverse effects with digoxin use is toxicity, and levels should be carefully monitored. Toxicity may manifest itself as GI effects (nausea, vomiting, and anorexia), CNS effects (headache, visual disturbances, malaise), hyperkalemia, and arrhythmias. Other effects reported include gynecomastia, vaginal changes, and local cutaneous reactions.
Common Clinical Applications: Effective in the management of congestive heart failure, to control ventricular rate in patients with atrial fibrillation and flutter, and to treat and prevent paroxysmal atrial tachycardia.















