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Dosing regimen for digoxin-specific antibody (Fab) fragments in patients with digoxin toxicity

Authors
Michael Levine, MD
Ayrn O'Connor, MD
Section Editors
Stephen J Traub, MD
Michele M Burns, MD, MPH
Deputy Editor
Jonathan Grayzel, MD, FAAEM

INTRODUCTION

Digoxin-specific antibody (Fab) fragments are the definitive treatment for patients with severe digitalis poisoning.

Prior to the advent of digoxin-specific antibodies, treatment for cardiac glycoside toxicity was largely supportive [1]. In 1976, antibody fragments were first used successfully to treat patients [2]. These antibodies are highly effective, safe, and widely used in clinical practice [3].

The dosing of digoxin-specific antibody (Fab) fragments based upon different clinical scenarios is discussed here. The indications for treatment with Fab fragments, the diagnosis and general management of digitalis poisoning, and the clinical use of digitalis are all reviewed separately. (See "Digitalis (cardiac glycoside) poisoning", section on 'Antidotal therapy with antibody (Fab) fragments' and "Use of digoxin in heart failure with reduced ejection fraction" and "Control of ventricular rate in atrial fibrillation: Pharmacologic therapy", section on 'Digoxin' and "Treatment with digoxin: Initial dosing, monitoring, and dose modification".)

WHAT ARE FAB FRAGMENTS?

Digoxin-specific antibody (Fab) fragments are purified preparations consisting of the Fab portion of IgG antidigoxin antibodies derived from immunized sheep. These fragments bind free digoxin, thereby forming digoxin-immune fragment complexes. As the level of free digoxin in plasma falls, the resulting concentration gradient facilitates dissociation of digoxin from the sodium-potassium ATPase. Digoxin-immune fragment complexes are renally excreted. Because the size of the digoxin-immune complex molecule is large, hemodialysis is not an effective means of removal.

KINETICS AND ADVERSE EFFECTS OF FAB FRAGMENTS

Fab fragments are commercially available as DigiFab [4]. Each vial of DigiFab contains 40 mg of Fab fragments and binds approximately 0.5 mg of digoxin. DigiFab has an elimination half-life of approximately 15 to 20 hours. However, the half-life may be up to 10 times longer with renal impairment. The volume of distribution for DigiFab 0.3 L/kg.

          

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Literature review current through: Jul 2017. | This topic last updated: Aug 15, 2017.
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