| Name: |
DIGOXIN (LanoxinR) |
| Classification: |
cardiac glycoside
- used in treatment of atrial fibrillation, atrial flutter, atrial tachycardia
- positive inotrope, negative chronotrope, negative dromotrope
- used to improve cardiac output in congestive heart failure
|
| Dose: |
- for congestive heart failure:
- loading dose: 8 - 10 mcg/kg lean body weight
- half of total dose given as first dose and additional fractions are given at 6 to 8 hour intervals
- maintenance dose:
- 1/3 of loading dose given once per day
- for atrial fibrillation:
- loading dose: 10 - 15 mcg/kg lean body weight administered as above
Reduce dosage in renal failure, hypothyroidism
| Creatinine Clearance |
Dose Reduction |
|
10-50 mL/minute
(0.17-0.84 mL/second)
|
Administer 25-75% of daily dose divided at normal intervals or give the normal dose every 36 hours. |
|
Less than 10 mL/minute
(0.17 mL/second)
|
Administer 10-25% of daily dose divided at normal intervals or give the normal dose every 48 hours. |
IV conversion dose is generally 80% of oral dose
|
| Administration: |
IV Direct:
- Mix in 50 mL of D5W or NS and administer over 5 - 10 minutes
- dilute with four times or greater volume to avoid precipitation
- onset of action 5 - 30 minutes post IV bolus
- rapid infusion may cause systemic or coronary artery vasoconstriction
|
| Adverse Effects: |
Symptoms of Toxicity:
Cardiac effects:
- every type of arrhythmia or AV block (sinus bradycardia or sinus rhythm with AV block, PAT with block, atrial fibrillation with complete heart block very suggestive of digoxin toxicity)
- risk factors:
- potassium/magnesium deficiencies or hypercalcemia increase risk of toxicity
- febrile or hypermetabolism-induced atrial arrhythmias may be resistant to digoxin, predisposing to toxicity
- gastrointestinal effects: anorexia, nausea, vomiting, diarrhea(common early signs of toxicity)
- CNS: headache, fatigue, lethargy, drowsiness, generalized muscle weakness, vertigo, neuralgia
- Occular: 'yellow and green' halo vision, diplopia, photophobia, blurred vision
Effects on potassium:
- chronic toxicity: hypokalemia
- acute toxicity: hyperkalemia
- Low magnesium, low potassium and hypercalcemia predispose patient to digoxin toxicity
|
| Antidote: |
Antidote for digoxin toxicity: Digoxin Immune Fab (Ovine) |
| Drug Interactions: |
- Reduce dosage in renal failure and hypothyroidism
- In renal failure
- beta blockers + digoxin = increased digoxin toxicity, decreased inotropic effect
- calcium + digoxin = increased risk of arrhythmias
- verapamil + digoxin = increased digoxin level
- propafenone + digoxin = decreased inotropic effect
- quinidine + digoxin = increased digoxin level
- rifampin + digoxin = decreased digoxin level
- sympathomimetics + digoxin = increased risk of arrhythmias
- drugs which cause hypokalemia = increased risk of digoxin toxicity
|
| Monitoring Therapy: |
- continuous heart rate and rhythm for acutely ill patients or during loading
- PR interval
- blood pressure
- potassium, magnesium and calcium levels
- urea, creatinine
- urine output
- routine levels not indicated; dosage adjustments should be based on symptomatology
- for chronic dosing, check pulse rate prior to administration of each dose
|
| Adult Critical Care Protocol: |
- May be administered IV direct or by IV infusion by a nurse in Adult Critical Care
- Continuous infusions must be administered by infusion device and the pump library must be enabled.
|
