Dosing and uses of Lanoxin (digoxin)
Adult dosage forms and strengths
oral solution
- 0.05mg/mL
injectable solution
- 0.1mg/mL
- 0.25mg/mL
tablet
- 0.0625mg (Lanoxin only)
- 0.125mg
- 0.1875mg (Lanoxin only)
- 0.25mg
Atrial Fibrillation
Rapid digitalizing (loading-dose) regimen
- IV: 8-12 mcg/kg (0.008-0.012 mg/kg) total loading dose; administer 50% initially; then may cautiously give 1/4 the loading dose q6-8hr twice; perform careful assessment of clinical response and toxicity before each dose
- PO: 10-15 mcg/kg total loading dose; administer 50% initially; then may cautiously give 1/4 the loading dose q6-8hr twice; peform careful assessment of clinical response and toxicity before each dose
Maintenance
- PO: 3.4-5.1 mcg/kg/day or 0.125-0.5 mg/day PO; may increase dose every 2 weeks based on clinical response, serum drug levels, and toxicity
- IV/IM: 0.1-0.4 mg qDay; IM route not preferred due to severe injection site reaction
Heart Failure
As per ACCF/AHA guidelines, a loading dose to initiate digoxin therapy in patients with heart failure is not necessary
0.125-0.25 mg PO/IV qDay; higher doses including 0.375-0.5 mg/day rarely needed
Use lower end of dosing (0.125 mg/day) in patients with impaired renal function or low lean body mass
Dosing Modifications
Adjust maintenance dose by estimating CrCl and measuring serum levels
In heart failure, higher dosages have no additional benefit and may increase toxicity; decreased renal clearance may lead to increased toxicity
In geriatric patients, use lean body weight to calculate dose
Pediatric dosage forms and strengths
oral solution
- 0.05mg/mL
injectable solution
- 0.1mg/mL
- 0.25mg/mL
tablet
- 0.125mg
- 0.25mg
Heart Failure/Atrial Fibrillation
Use doses at the lower end of the spectrm when treating heart failure
Reduce dose by 20-25% when changing from oral formulation or IM to IV therapy
Premature neonate
- PO: 1st loading dose, 10-15 mcg/kg; 2nd and 3rd loading doses, 5-7.5 mcg/kg q6-8hr for 2 doses; maintenance: 5-7.5 mcg/kg/day divided q12hr
- IV/IM: 1st loading dose, 7.5-12.5 mcg/kg; 2nd and 3rd loading doses, 3.75-6.25 mcg/kg q6-8hr for 2 doses; maintenance: 4-6 mcg/kg/day divided q12hr
Full-term neonate
- PO: 1st loading dose, 12.5-17.5 mcg/kg; 2nd and 3rd loading doses, 6.25-8.75 mcg/kg q6-8hr for 2 doses; maintenance: 6-10 mcg/kg/day divided q12hr
- IV/IM: 1st loading dose, 10-15 mcg/kg; 2nd and 3rd loading doses, 5-7.5 mcg/kg q6-8hr for 2 doses; maintenance: 5-8 mcg/kg/day divided q12hr
Infants & children 1-24 months
- PO: 1st loading dose, 17.5-30 mcg/kg; 2nd and 3rd loading doses, 8.75-15 mcg/kg q6-8hr for 2 doses; maintenance: 10-15 mcg/kg/day divided q12hr
- IV/IM: 1st loading dose, 15-25 mcg/kg; 2nd and 3rd loading doses, 7.5-12.5 mcg/kg q6-8hr for 2 doses; maintenance: 7.5-12 mcg/kg/day divided q12hr
2-5 years
- PO: 1st loading dose, 15-20 mcg/kg; 2nd and 3rd loading doses, 8.75-10 mcg/kg q6-8hr for 2 doses; maintenance: 7.5-10 mcg/kg/day divided q12hr
- IV/IM: 1st loading dose, 12.5-17.5 mcg/kg; 2nd and 3rd loading doses, 6.25-8.75 mcg/kg q6-8hr for 2 doses; maintenance: 6-9 mcg/kg/day divided q12hr
5-10 years
- PO: 1st loading dose, 10-17.5 mcg/kg; 2nd and 3rd loading doses, 5-8.75 mcg/kg q6-8hr for 2 doses; maintenance: 5-10 mcg/kg/day divided q12hr
- IV/IM: 1st loading dose, 7.5-15 mcg/kg; 2nd and 3rd loading doses, 3.75-7.5 mcg/kg q6-8hr for 2 doses; maintenance: 4-8 mcg/kg/day divided q12hr
>10 years & <100 kg
- PO: 1st loading dose, 5-7.5 mcg/kg; 2nd and 3rd loading doses, 2.5-3.75 mcg/kg q6-8hr for 2 doses; maintenance: 2.5-5 mcg/kg/day
- IV/IM: 1st loading dose, 4-6 mcg/kg; 2nd and 3rd loading doses, 2-3 mcg/kg q6-8hr for 2 doses; maintenance: 2-3 mcg/kg/day
Lanoxin (digoxin) adverse (side) effects
1-10%
Dizziness (4.9%)
Mental disturbances (4.1%)
Diarrhea (3.2%)
Headache (3.2%)
Nausea (3.2%)
Vomiting (1.6%)
Maculopapular rash (1.6%)
<1%
Anorexia
Cardiac dysrhythmia
Arrhythmia in children (consider a toxicity)
Frequency not defined
Visual disturbance (blurred or yellow vision)
Heart block (1°/2°/3°)
Asystole
Tachycardia
Warnings
Contraindications
Hypersensitivity
Ventricular fibrillation
Cautions
Use caution in chronic constrictive pericarditis, electrical cardioversion, severe bradycardia, severe heart failure, severe pulmonary disease, sick sinus syndrome, ventricular tachycardia, ventricular premature contractions, Wolff-Parkinson-White syndrome, electrolyte imbalance, hypothyroidism or hyperthyroidism, hypoxia, idiopathic hypertrophic subaortic stenosis, renal disease, concomitant diuretics
Not recommended in patients with acute myocardial infarction
Avoid in patients with myocarditis
Risk of advanced or complete heart block in patients with sinus node disease and AV block
Very narrow margin between effective therapeutic and toxic dosages: Therapeutic range, 0.5-2 ng/mL (target 0.5-1 ng/mL); toxic range, >2.5 ng/mL
Generally avoid if left ventricular systolic function preserved, although may be used for ventricular rate control in subgroup with chronic atrial fibrillation
Less effective in presence of hypokalemia or hypocalcemia; avoid hypercalcemia or hypomagnesemia, which may predispose to serious arrhythmias
Heart failure patients with preserved ventricular function including acute cor pulmonale, amyloid heart disease, and constrictive pericarditis may be susceptible to digoxin toxicity
May cause false-positive ST-T changes during exercise testing
Do not switch between different PO forms or between brand and generic forms of digoxin; bioavailability varies
Serum levels drawn within 6-8 hours of dose will be falsely high because of prolonged distribution phase
Increased risk of estrogenlike effects in geriatric patients
Beriberi heart disease may not respond adequately if underlying thiamine deficiency not corrected
Atrial arrhythmias are difficult to treat if associated with hypermetabolic (hyperthyroidism) or hyperdynamic (hypoxia) states; treat underlying condition before initiating therapy
Avoid extravasation; ensure proper needle or catheter placement prior to and during administration
Monitor for proarrhythmic effects, especially with digoxin toxicity
Use caution in patients with acute myocardial infarction; may increase myocardial oxygen demand; during acute coronary syndrome, digoxin administered IV may be used to slow a rapid ventricular response and improve left ventricular function in the acute treatment of atrial fibrillation associated with severe LV function and heart failure or hemodynamic instability
Monitor serum concentration closely when used for rate control in patients with atrial fibrillation; serum concentration that are not properly conrolled are associated with increased risk of mortality
Consider use of digoxin only in heart failure with reduced ejection fraction when symptoms remain despite guideline-directed medical therapy; withdrawal of digoxin in clinically stable patients with heart failure may lead to recurrence of heart failure symptoms
In hyperophic cariomyopathy, outflow obstruction may worsen due to positive inotropic effects of digoxin; avoid use unless used to control ventricular response with atrial fibrillation; in the absence of atrial fibrillation, digoxin is potentially harmful in the treatment of dyspnea in patients with hypertrophic cardiomyopathy
Avoid rapid IV administration in digitalized patients; may produce serious arrhythmias
Not necessary to routinely reduce or hold digoxin therapy prior to elective electrical cardioversion for atrial fibrillation; however, exclusion of digoxin toxicity is necessary prior to cardioverstion; whithhold digoxin and delay caridioversion until toxicity subsides if signs of digoxin excess exist
Pregnancy and lactation
Pregnancy category: C
Lactation: Drug enters breast milk; use with caution (American Academy of Pediatrics committee states, "compatible with nursing")
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Lanoxin (digoxin)
Mechanism of action
In heart failure, increases contractility by inhibiting sodium/potassium ATPase pump in myocardial cells, which subsequently promotes calcium influx via sodium-calcium exchange pump
In supraventricular arrhythmias, suppresses AV node conduction, which increases refractory period and decreases conduction velocity, causing positive inotropic effect, decreased ventricular rate, and enhanced vagal tone
Absorption
Bioavailability: 60-80 % (tablet); 70-85% (elixir)
Onset: 0.5-2 hr (PO) for initial effect and 2-6 hr for maximal effect; 5-30 min (IV) for initial effect and 1.5-4 hr for maximal effect
Duration: 3-4 days
Peak serum time: 1-3 hr (PO)
Distribution
Protein bound: 20-25%
Vd: 6-7 L/kg
Metabolism
Metabolized by liver
Metabolites: Digoxigenin bisdigitoxoside, digoxigenin monodigitoxoside (active)
Elimination
Half-life: 1-3 days
Excretion: Urine (57-80%), feces (9-13%; includes bile)
Administration
IV Compatibilities
Solution: D5/½NS with potassium chloride 20 mEq, D5W, LR, ½NS, Ns
Additive: Bretylium, cimetidine, floxacillin, furosemide, lidocaine, ranitidine, verapamiL
Syringe: Heparin, milrinone
Y-site: Bivalirudin, ciprofloxacin, cisatracurium, dexmedetomidine, diltiazem, famotidine, fenoldopam, gatifloxacin, heparin with hydrocortisone, Hextend, inamrinone, linezolid, meperidine, meropenem, midazolam, milrinone, morphine sulfate, potassium chloride, remifentanil, tacrolimus, vitamins B and C
IV Incompatibilities
Additive: Dobutamine
Syringe: Doxapram
Y-site: Amphotericin B cholesteryl sulfate, amiodarone, fluconazole, foscarnet, insulin (beef, pork, and Humulin R[?]), propofoL
IV Preparation
Dilute with 4-fold or greater volume of SWI, D5W, or Ns
IV Administration
Administer slowly by direct IV injection over minimum of 5 minutes (longer if given undiluted)
Do not administer if precipitate present
Drug is severe skin irritant when given IV/IM and may cause severe local skin reaction with possible sloughing
Storage
Store at controlled room temperature
Protect from light
