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Trade Names:
Digitek
- Tablets 0.125 mg
- Tablets 0.25 mg

Trade Names:
Digoxin
- Elixir, pediatric 0.05 mg/mL

Trade Names:
Lanoxicaps
- Capsules 0.05 mg
- Capsules 0.1 mg
- Capsules 0.2 mg

Trade Names:
Lanoxin
- Tablets 0.125 mg
- Tablets 0.25 mg
- Injection 0.25 mg/mL
- Injection, pediatric 0.1 mg/mL

Mechanism of Action

Pharmacology

Increases force and velocity of myocardial systolic contraction (positive inotropic action), slows heart rate, and decreases conduction through atrioventricular node.

Pharmacokinetics

Absorption

100% (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

Cl correlates with Ccr. 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

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.

Individualize dosage. Usual doses in children are listed at end of section.

General Advice

• For IV administration, digoxin injection may be diluted (up to 4-fold) 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

May increase digoxin serum levels.

May decrease absorption and effect of digoxin.

May decrease effect of digoxin.

May alter effect of digoxin.

May increase effect of digoxin.

May 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

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.

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.