Digoxin
Pronunciation: (dih-JOX-in)Class: Cardiac glycoside
Trade Names:
Digoxin
- Elixir, pediatric 0.05 mg/mL
Trade Names:
Lanoxicaps
- Capsules 0.1 mg
Trade Names:
Lanoxin
- Tablets 0.125 mg
- Tablets 0.25 mg
- Injection 0.25 mg/mL
- Injection, pediatric 0.1 mg/mL
Digoxin Injection C.S.D. (Canada)
Digoxin Pediatric Injection C.S.D. (Canada)
PMS-Digoxin (Canada)
Pharmacology
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Increases force and velocity of myocardial systolic contraction (positive inotropic action), slows heart rate, and decreases conduction through atrioventricular node.
Pharmacokinetics
Absorption
Bioavailability100% (IV), 90% to 100% (capsules), 70% to 85% (elixir), 60% to 80% (tablets). T max is 1 to 3 h (oral). Food slows the rate of absorption after oral administration.
Distribution
6 to 8 h tissue distribution phase. Large apparent Vd. Crosses blood-brain barrier and placenta. Excreted in breast milk. Approximately 25% protein bound.
Metabolism
Approximately 16% metabolized; metabolites formed by hydrolysis, oxidation, and conjugation.
Elimination
Elimination follows first-order kinetics. 50% to 70% excreted unchanged in the urine (after IV administration). t ½ is 1.5 to 2 days.
Onset
0.5 to 2 h (oral), 5 to 30 min (IV).
Peak
2 to 6 h (oral), 1 to 4 h (IV).
Special Populations
Renal Function ImpairmentCl correlates with CrCl. Dosage adjustment recommended.
Indications and Usage
Treatment of CHF, atrial fibrillation, atrial flutter, paroxysmal atrial tachycardia, cardiogenic shock.
Contraindications
Ventricular fibrillation; ventricular tachycardia except in certain cases; digitalis toxicity; beriberi heart disease; hypersensitivity to digoxin; some cases of hypersensitive carotid sinus syndrome.
Dosage and Administration
Rapid digitalization with loading doseAdults
IV 0.4 to 0.6 mg or PO tablets 0.5 to 0.75 mg or capsules 0.4 to 0.6 mg in previously undigitalized patients; additional doses may be given cautiously at 6 to 8 h intervals ( IV 0.1 to 0.3 mg or PO tablets 0.125 to 0.375 mg or capsules 0.1 to 0.3 mg) until clinical response is achieved; thereafter adjust dosage based on levels (usual range 0.125 to 0.5 mg/day as single daily dose). In previously digitalized patients, adjust dosage in proportion to ratio of desired vs current serum levels.
Infants and childrenIndividualize dosage. Usual doses in children are listed at end of section.
General Advice
- For IV administration, digoxin injection may be diluted (4-fold or more) with normal saline, D5W, or sterile water for injection. Infuse slowly, over 5 min or longer.
- Do not mix digoxin solution with other drugs.
Drug Interactions
Amiodarone, anticholinergics, bepridil, benzodiazepines, ACE inhibitors, clarithromycin, cyclosporine, diltiazem, erythromycin, indomethacin, itraconazole, propafenone, quinidine, quinine, tetracycline, verapamilMay increase digoxin serum levels.
Antacids, antineoplastics, cholestyramine, colestipol, kaolin/pectin, metoclopramideMay decrease absorption and effect of digoxin.
PenicillamineMay decrease effect of digoxin.
Potassium-sparing diureticsMay alter effect of digoxin.
Thiazide or loop diureticsMay increase effect of digoxin.
St. John's wort, thyroid hormones, thioamidesMay decrease effect of digoxin.
Laboratory Test Interactions
None well documented.
Adverse Reactions
Cardiovascular
Arrhythmias (supraventricular arrhythmias are more common in infants and children), including ventricular tachycardia and premature ventricular contractions.
CNS
Headache; weakness; apathy; drowsiness; mental depression; confusion; disorientation.
EENT
Visual disturbances (eg, blurred vision, halo effect).
GI
Anorexia; nausea; vomiting; diarrhea.
Precautions
MonitorMonitor apical pulse for 1 full min before administering. Withhold dose and notify health care provider if pulse rate is less than 60 bpm in adult, less than 70 bpm in child, or less than 90 bpm in infant. Note signs of toxicity occur (eg, abdominal pain, anorexia, nausea, vomiting, visual disturbance, bradycardia, ECG changes, arrhythmias, headache, seizure). Be prepared to administer digoxin antibodies (digoxin-immune Fab) for severe overdose toxicity. |
Pregnancy
Category C .
Lactation
Excreted in breast milk.
Children
Newborns show varying tolerance. Premature and immature infants are particularly sensitive; reduce and individualize dose as needed.
Elderly
Use with caution; renal Cl likely to be reduced.
Renal Function
Excretion may be decreased, leading to digoxin accumulation and toxicity; adjust dosage.
CV disease
Electrical conversion of arrhythmias may require dose reduction.
Digitalis toxicity
Anorexia, nausea, and vomiting may be associated with toxicity or CHF. Arrhythmias for which digoxin is indicated may also be a reflection of toxicity.
Electrolyte imbalance
Maintain normal serum potassium, calcium, and magnesium levels.
Lanoxicaps
Lanoxicaps have greater bioavailability than standard tablets. The 0.2 mg capsule is equivalent to 0.25 mg tablet; the 0.1 mg capsule to 0.125 mg tablet; the 0.05 mg capsule to 0.0625 mg tablet.
Usual Pediatric Digitalizing and Maintenance Dosages With Normal Renal Function Based on Lean Body Weight Age Digitalizing Dose (mcg/kg) Daily Maintenance Dose as % of Loading Dose (mcg/kg in 2 to 3 divided doses) PO IV Premature 20 to 30 15 to 25 20% to 30% Term 25 to 35 20 to 30 25% to 35% 1 to 24 mo 35 to 60 30 to 50 25% to 35% 2 to 5 yr 30 to 40 25 to 35 25% to 35% 5 to 10 yr 20 to 35 15 to 30 25% to 35% > 10 yr 10 to 15 8 to 12 25% to 35%Overdosage
Symptoms
GI tract (eg, anorexia, nausea, vomiting, diarrhea); nervous system (eg, headache, weakness, apathy, drowsiness, visual disturbances such as blurred, yellow or green vision, halo effect), depression, confusion, restlessness, disorientation, seizures, EEG abnormalities, delirium, hallucinations, neuralgia and psychosis; cardiovascular system (eg, ventricular tachycardia, PVCs, paroxysmal and nonparoxysmal nodal rhythms, AV dissociation, accelerated nodal rhythm and premature atrial contraction with block, atrial fibrillation, ECG changes, all alterations in cardiac rate and rhythm). Conduction disturbances are common manifestations of toxicity in children.
Patient Information
- Instruct patient to take digoxin at same time each day to ensure steady-state dosing and to contact health care provider for instructions if dose is missed.
- Teach patient and family name, action, administration, adverse reactions, and toxic effects of particular digoxin preparation.
- Emphasize importance of regular follow-up exams to determine effectiveness and to monitor for toxicity.
- Caution patient to avoid taking otc medications without consulting health care provider. Antacids and antidiarrheals, for example, slow absorption of digoxin.
- Teach patient and family to take pulse and to seek health care provider's advice for rates less than 60 bpm or more than 100 bpm (adults).
- If patient is directed by health care provider, help identify ways to supplement potassium intake.
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digoxin - Includes detailed dosage instructions.
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Atrial Fibrillation, Heart Failure
