digoxin immune Fab

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digoxin

 [dĭ-jok´sin]
a cardiotonic glycoside obtained from the leaves of Digitalis lanata; used in the treatment of congestive heart failure. It has a relatively rapid action and rapid elimination.
digoxin immune Fab (ovine) see under Fab.

Fab

 (fragment, antigen-binding)
originally, either of two identical fragments, each containing an antigen combining site, obtained by papain cleavage of the IgG molecule; now generally used as an adjective in terms such as Fab fragment or region, referring to an “arm” of any immunoglobulin monomer, i.e., one light chain and the adjoining heavy chain VH and CH1 domains.
digoxin immune Fab (ovine) a preparation of antigen-binding fragments derived from specific antidigoxin antibodies produced in sheep that have been immunized with digoxin coupled as a hapten to human serum albumin, used as an antidote to life-threatening digoxin and digitoxin overdose; administered intravenously.

digoxin immune Fab

(di-jox-in im-myoon fab) ,

Digibind

(trade name),

DigiFab

(trade name)

Classification

Therapeutic: antidotes
Pharmacologic: antibody fragments
Pregnancy Category: C

Indications

Serious life-threatening overdosage with digoxin.

Action

An antibody produced in sheep that binds antigenically to unbound digoxin in serum.

Therapeutic effects

Binding and subsequent removal of digoxin, preventing toxic effects in overdose.

Pharmacokinetics

Absorption: Administered IV only, resulting in complete bioavailability.
Distribution: Widely distributed throughout extracellular space.
Metabolism and Excretion: Excreted by the kidneys as the bound complex (digoxin immune Fab plus digoxin).
Half-life: 14–20 hr.

Time/action profile (reversal of arrhythmias and hyperkalemia; reversal of inotropic effect may take several hr)

ROUTEONSETPEAKDURATION
IV30 min (variable)unknown2–6 hr

Contraindications/Precautions

Contraindicated in: No known contraindications.
Use Cautiously in: Known hypersensitivity to sheep proteins or products;Children, pregnancy, or lactation (safety not established).

Adverse Reactions/Side Effects

Cardiovascular

  • re-emergence of atrial fibrillation
  • re-emergence of HF

Fluid and Electrolyte

  • hypokalemia (life-threatening)

Interactions

Drug-Drug interaction

Prevents therapeutic response to digoxin.

Route/Dosage

Digibind—38 mg of digoxin immune Fab will bind 0.5 mg of digoxin. Each vial contains 38 mg of digoxin immune Fab; DigiFab—40 mg of digoxin immune Fab will bind 0.5 mg of digoxin. Each vial contains 40 mg of digoxin immune Fab

Known Amount of Digoxin Ingested (Administered)

Intravenous (Adults and Children) For digitalis glycoside toxicity due to digoxin tablets, oral solution, or IM digoxin—dose of digoxin ingested (mg) × 0.8/1000 × 38. For digitalis glycoside toxicity due to digoxin capsules, IV digoxin—dose of digoxin ingested (mg)/0.5 × 38.

Known Serum Digoxin Concentrations (SDCs)

Intravenous (Adults and Children) Digibind—Dose (mg)=SDC (nanograms/mL) × body weight (kg)/100 × 38; DigiFab—SDC (nanograms/mL) × body weight (kg)/100 × 40.

Unknown Amount Ingested/SDCs Unavailable

Intravenous (Adults and Children) Digibind—760 mg (20 vials); DigiFab—800 mg (20 vials).

Toxicity during chronic digoxin therapy

Intravenous (Adults and Children) Digibind—228 mg (6 vials); DigiFab—240 mg (6 vials).

Availability

Powder for injection, lyophilized (Digibind): 38 mg/vial
Powder for injection, lyophilized (DigiFab): 40 mg/vial

Nursing implications

Nursing assessment

  • Monitor ECG, pulse, BP, and body temperature before and during treatment. Patients with atrial fibrillation may develop a rapid ventricular response as a result of decreased digoxin levels.
  • Assess patient for increase in signs of HF (peripheral edema, dyspnea, rales/crackles, weight gain).
  • Lab Test Considerations: Monitor serum digoxin levels before administration.
    • Monitor serum potassium levels frequently during treatment. Before treatment, hyperkalemia usually coexists with toxicity. Levels may decrease rapidly; hypokalemia should be treated promptly.
    • Free serum digoxin levels fall rapidly after administration. Total serum concentrations rise suddenly after administration but are bound to the Fab molecule and are inactive. Total serum concentrations will decrease to undetectable levels within several days. Serum digoxin levels are not valid for 5–7 days after administration.

Potential Nursing Diagnoses

Deficient knowledge, related to medication regimen (Patient/Family Teaching)

Implementation

  • Cardiopulmonary resuscitation equipment and medications should be available during administration.
    • Delay redigitalization for several days until the elimination of digoxin immune Fab from the body is complete.
  • Intravenous Administration
  • pH: 6.0–8.0.
  • Intermittent Infusion: Diluent: Reconstitute each vial in 4 mL of sterile water for injection and mix gently. Solution will contain a concentration of 9.5 mg/mL (Digibind) or 10 mg/mL (DigiFab). May be further diluted with 0.9% NaCl to achieve the concentration below. Reconstituted solution should be used immediately but is stable for 4 hr if refrigerated. For small doses in infants and children, a reconstituted 38-mg vial can be diluted with 34 mL of 0.9% NaCl (Digibind) or 36 mL of 0.9% NaCl (DigiFab) for a concentration of 1 mg/mL. Concentration: 1 mg/mL.
  • Rate: Infuse over 30 min through a 0.22-micron membrane filter. If cardiac arrest is imminent, rapid direct IV injection may be used. Do not use rapid direct injection in other patients because of increased risk of adverse reactions. Small doses in infants and children may be administered with a tuberculin syringe.
  • Incompatibility: Information unavailable. Do not mix with other drugs or solutions.

Patient/Family Teaching

  • Explain the procedure and purpose of the treatment to the patient.
  • Instruct patient to notify health care provider immediately if signs of delayed allergic reaction (rash, pruritus, urticaria) occur after hospital discharge.

Evaluation/Desired Outcomes

  • Resolution of signs and symptoms of digoxin toxicity.
    • Decreased digoxin or level without major side effects.

digoxin immune FAB, ovine

a preparation of antigen-binding fragments derived from specific antidigoxin antibodies produced in sheep that have been immunized with digoxin coupled as a hapten to human serum albumin. It is used as an antidote to life-threatening digoxin and digitoxin overdose and is administered intravenously.
indications It is prescribed for the treatment of life-threatening digoxin or digitoxin toxicity.
contraindications Use of this product should be restricted to patients who are in shock or cardiac arrest or show signs of severe ventricular arrhythmias, progressive bradycardia, or potassium concentrations exceeding 5 mEq/L.
adverse effects Among reported adverse reactions are low cardiac output, congestive heart failure exacerbated by withdrawal of the inotropic effect of digoxin, rapid ventricular response caused by withdrawal of the digitalis effect, and possible hypokalemia.