Description

Digoxin is a digitalis glycoside that has a direct effect on cardiac muscle and the electrical conduction in the heart. It increases cardiac output by increasing myocardial contractility. Digoxin helps decrease sympathetic tone, and as a result, causes increased diuresis and a reduction of edema. This results in a reduction of heart size, heart rate, blood volume, and pulmonary and venous pressures.

Usage

Digoxin is used in the treatment of congestive heart failure in horses, usually in conjunction with other medications, including diuretics, and angiotensin convertin (ACE) inhibitors.

Dosage and Administration

Cyproheptadine
Method	Dosage (click row for calculator)	Concentration	Period	Duration
Oral	0.011 mg/kg	0.250 mg/tablet	Twice daily	NA
Intravenous injection	0.0022 mg/kg	0.25 mg/ml	Twice daily	NA
Notes: Federal law restricts this drug to use by or on the order of a licensed veterinarian. Extra-label use of drugs in treating animals is allowable only by licensed veterinarians within the context of a valid veterinarian-client-patient relationship, and does not include drug use in treating animals by the layman (except under the supervision of a licensed veterinarian). Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

The most common side effects are due to digitalis toxicity that may result in arrhythmias, including heart block paroxysmal atrial, or ventricular tachycardias, and multifocal premature ventricular contractions.

Digitalis toxicity may lead to gastrointestinal side effects, including anorexia, nausea, and diarrhea.

Other side effects include central nervous system disturbances, unsteady gait, and depression.

Precautions

Use of digitoxin requires careful monitoring under the direction of a veterinarian. With a narrow margin of safety and a significant variation in absorption among horses, prevention of toxicity is very important.

Digoxin is excreted by the kidneys and the dose may need to be lowered for horses with renal disease.

Digoxin should not be used in horses with ventricular fibrillation or digitalis intoxication.

Digoxin is not FDA approved for use in horses, but is common accepted practice. U. S. federal law restricts this drug to use by or on the lawful written or oral order of a licensed veterinarian.

Digoxin is either a regulated or prohibited substance in most sanctioned competitions. It is important to check with the proper individual regulatory group.

Interactions

Antacids, cimetidine, metoclopramide, oral neomycin, and penicillamine may decrease digoxin absorption.

Diazepam, quinidine, anticholinergics, succinycholine, verapamil, tetracycline, and erythromycin may lead to increases in digoxin levels.

Drugs that decrease serum potassium may predispose horses to digoxin toxicity. They include diuretics, amphotericin B, corticosteroids, ACTH, some laxatives, glucagon, dextrose, or dextrose/insulin infusion, and sodium polystyrene sulfonate.

Overdose

Overdose may result in chronic toxicity with effects noted in above-listed side effects. Acute toxicity due to ingestion may be treated by emptying the stomach and using activated charcoal.