Lanoxin 250 mcg Tablets

Brand Name

The medication is marketed under the trade name Lanoxin, a label that has gained prominence in cardiovascular therapy. This designation is widely acknowledged among healthcare professionals and patients seeking treatment for specific heart-related conditions.

International Non-Proprietary Name (INN)

Lanoxin is identified worldwide by its international non-proprietary name, digoxin. This term denotes the active compound responsible for its therapeutic actions, ensuring its recognition remains consistent across various medical contexts and regions.

Form of Release

This drug is available in multiple forms to accommodate diverse patient needs, primarily as oral tablets and an injectable solution. Tablets are offered in strengths of 0.0625 mg, 0.125 mg, and 0.25 mg, while the injectable form comes in vials or ampules, typically at 0.25 mg/mL, allowing for both outpatient and acute care administration.

Composition

The principal active ingredient in Lanoxin is digoxin, a cardiac glycoside derived from the foxglove plant, known for its heart-strengthening properties. In tablets, it is accompanied by excipients such as lactose monohydrate, corn starch, magnesium stearate, and occasionally dyes like FD&C Yellow No. 6 for color differentiation. The injectable solution includes propylene glycol, citric acid, sodium phosphate, and water for injection, formulated to maintain stability and facilitate intravenous delivery.

Pharmacologic Properties

Pharmacodynamics

Lanoxin enhances cardiac performance by inhibiting the sodium-potassium ATPase enzyme in myocardial cells, increasing intracellular calcium availability. This action strengthens the force of heart contractions, improving output in weakened states. Simultaneously, it slows electrical conduction through the atrioventricular node, reducing heart rate and aiding rhythm control. These dual effects bolster its utility in managing conditions marked by inefficient pumping or irregular beats, offering a balanced approach to cardiac support.

Pharmacokinetics

Upon oral administration, digoxin in Lanoxin is absorbed from the gastrointestinal tract, with bioavailability ranging from 60% to 80%, influenced by food or gut motility. Peak plasma concentrations occur within 1 to 3 hours for tablets, or faster with injection. It distributes widely, with a volume of 5 to 7 L/kg, concentrating in heart, kidney, and skeletal muscle tissues, and binds modestly to plasma proteins at 20-25%. Metabolism is minimal, with most excretion occurring unchanged via the kidneys through glomerular filtration and tubular secretion. The elimination half-life averages 36 to 48 hours in patients with normal renal function, extending significantly in renal compromise.

Indications for Use

Diseases and Conditions

Lanoxin is indicated for the treatment of heart failure, particularly when systolic dysfunction impairs the heart’s ability to pump effectively. It is also employed to control ventricular rate in atrial fibrillation or atrial flutter, stabilizing rapid rhythms that could otherwise strain cardiac function. These applications underscore its role in supporting patients with chronic or symptomatic cardiac conditions, enhancing quality of life through improved circulation and rhythm regulation.

Contraindications

Conditions Prohibiting Use

Lanoxin is not suitable for individuals with a documented hypersensitivity to digoxin or related glycosides, as reactions might include rashes or severe anaphylaxis. It is contraindicated in patients with ventricular fibrillation, where its use could exacerbate life-threatening arrhythmias. Those with pre-existing atrioventricular block, particularly second- or third-degree without a pacemaker, should avoid it due to risks of complete heart block. Conditions like hypertrophic cardiomyopathy with outflow obstruction or acute myocarditis also preclude its administration, as enhanced contractility could worsen obstruction or inflammation-related damage.

Method of Administration and Dosage

Administration Guidelines

Lanoxin tablets are taken orally, with or without food, as absorption remains consistent regardless of meals. They should be swallowed whole with water, avoiding crushing to ensure proper dosing. The injectable form is administered intravenously by healthcare providers, often diluted in saline or dextrose, with slow infusion to prevent irritation or rapid onset of effects. Regular monitoring of serum digoxin levels, ideally 0.5-2 ng/mL, guides safe use.

Dosage for Adults and Children

For adults with heart failure, Lanoxin dosing often begins with a loading dose of 0.75 to 1.5 mg over 24 hours, split into smaller increments, followed by maintenance at 0.125 to 0.25 mg daily. In atrial fibrillation, similar loading may apply, with maintenance adjusted to heart rate response. Pediatric dosing is weight-based; neonates might receive 20-30 mcg/kg as a total loading dose, divided over 24 hours, with maintenance at 5-10 mcg/kg daily, while older children adjust closer to 10-15 mcg/kg, always under strict supervision due to sensitivity variations.

Dose Adjustment in Specific Conditions

Renal impairment requires significant dose reduction, as digoxin clearance drops with declining kidney function; maintenance might fall to 0.0625-0.125 mg daily in severe cases, guided by serum levels. Hepatic dysfunction has less impact, as metabolism is limited, though caution is advised in cirrhosis due to altered distribution. Elderly patients typically start at lower doses, such as 0.125 mg daily, reflecting reduced renal capacity and increased risk of accumulation, with frequent monitoring to optimize therapy.

Side Effects

Potential Adverse Reactions

Lanoxin can induce a range of side effects, often tied to its narrow therapeutic window. Gastrointestinal issues like nausea, vomiting, or appetite loss are common, as are central nervous system effects such as dizziness, headache, or blurred vision. Cardiac disturbances, including bradycardia or arrhythmias, may signal toxicity, particularly at higher doses. Fatigue, confusion, or mood changes occasionally occur, while rare skin reactions like rashes or yellowish vision (xanthopsia) have been noted. Most effects lessen with dose adjustment, though persistent symptoms require medical review.

Overdose

Symptoms of Overdose

Excessive Lanoxin intake can lead to toxicity, marked by severe nausea, vomiting, and profound fatigue. Cardiac signs include dangerously slow heart rates, irregular rhythms, or ventricular ectopic beats, potentially progressing to life-threatening arrhythmias. Neurological symptoms like confusion, delirium, or visual halos may emerge, alongside hyperkalemia in severe cases, reflecting cellular disruption. Immediate recognition of these signs is critical for timely intervention.

First Aid Measures

In an overdose situation, discontinue Lanoxin and seek urgent medical care. Activated charcoal may reduce absorption if given within hours of ingestion, while intravenous fluids support circulation. Digoxin-specific antibody fragments (Digibind) are the primary antidote, administered based on serum levels or estimated dose, neutralizing free digoxin. Potassium levels and heart rhythm require close monitoring, with temporary pacing considered for severe bradycardia until stability is restored.

Drug Interactions

Effects on Other Medications

Lanoxin interacts with numerous drugs, often via altered clearance or enhanced effects. Agents like verapamil, amiodarone, or quinidine increase digoxin levels by inhibiting P-glycoprotein or renal excretion, necessitating dose reductions. Diuretics, particularly loop or thiazide types, may exacerbate hypokalemia or hypomagnesemia, heightening toxicity risk. Concurrent use with beta-blockers or calcium channel blockers can amplify bradycardia, requiring careful rhythm monitoring. It has minimal impact on other drugs’ metabolism, as it is not a significant enzyme substrate.

Compatibility with Alcohol and Food

Alcohol use with Lanoxin should be limited, as it may worsen dehydration or electrolyte imbalances, indirectly increasing side effect risks. Food does not substantially affect absorption, though high-fiber meals might slightly delay it without clinical significance. Consistency in dietary potassium intake helps maintain stable drug effects, avoiding sudden shifts that could disrupt cardiac response.

Special Precautions

Use During Pregnancy and Breastfeeding

Lanoxin crosses the placenta, but extensive use in pregnancy shows no definitive teratogenic risk; it may be used if benefits justify potential fetal exposure, often for maternal heart conditions, with fetal monitoring advised. Digoxin enters breast milk in small amounts, generally considered safe for breastfeeding infants, though nursing mothers should observe for unusual symptoms and consult providers if concerns arise.

Impact on Driving and Operating Machinery

Lanoxin may impair driving or machinery operation if dizziness, vision changes, or fatigue occur, particularly during initiation or dose changes. Patients should assess their response before engaging in such tasks, refraining if affected, to ensure safety until acclimated to the medication’s effects.

Considerations for Elderly and Pediatric Populations

Elderly patients often exhibit greater sensitivity to Lanoxin, with reduced renal clearance raising toxicity risks, warranting lower doses and vigilant monitoring. In children, its use is common for congenital heart issues, with dosing tailored to age and weight, requiring precision due to variable pharmacokinetics and narrow safety margins. Both groups benefit from individualized care to balance efficacy and minimize adverse outcomes.