DIGIFab

Frequently Asked Questions
About DIGIFab

Does the infusion rate and total infusion time for DIGIFab differ depending on the dose administered?

The package insert for DIGIFab states, “Administer DIGIFab slowly as an intravenous infusion over at least 30 minutes. Stop the infusion if infusion rate–related reactions occur. The infusion can be restarted at a slower rate. If cardiac arrest is imminent, DIGIFab can be given by bolus injection. An increased incidence of infusion-related reactions may be expected with bolus injection.” The infusion rate and duration recommendations in the package insert relate to the entire dose, regardless of how many vials are administered.1

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Is the dosing of DIGIFab different between adults and children?

The method of determining the dose of DIGIFab is the same for adults and children and is based on the total body burden of digoxin, which is calculated from the patient’s weight and steady-state serum concentration of digoxin. For infants and small children who may require very small doses, it is recommended that the
40-mg vial be reconstituted as directed and administered undiluted using a tuberculin syringe. For toxicity during chronic digoxin therapy, and an unknown serum digoxin concentration, 6 vials of DIGIFab is recommended for adults, while for infants and small children (<20 kg) the recommended dose is 1 vial.1

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Is there latex in DIGIFab or in the DIGIFab vial stopper?

DIGIFab does not contain latex. However, papain is used to manufacture DIGIFab and trace amounts of papain may be present in the product.1 While papain allergy is not a contraindication to the use of DIGIFab,1 it has been noted in the literature that latex and dust mite allergens share antigenic structures with papain and that patients with allergies to latex or dust mites may also be allergic to papain2,3; these patients therefore have the potential to have an allergic reaction to DIGIFab.1 If a patient has a known life-threatening hypersensitivity reaction to latex, the risk-benefit profile of administration should be evaluated.1

Should skin testing be performed prior to administering DIGIFab?

Skin testing was not performed in the clinical trials of DIGIFab, is not a recommendation within the DIGIFab package insert, and is not required before its administration.1

Can DIGIFab be readministered?

If toxicity has not adequately reversed after several hours, or appears to recur, readministration of DIGIFab, at a dose guided by clinical judgment, may be necessary. If a patient is in need of readministration of DIGIFab due to recurrent toxicity, or to a new toxic episode that occurs soon after the first episode, measurement of free (unbound) serum digoxin concentrations should be considered since Fab may still be present in the body.1

Is there a generic version of DIGIFab?

No, there is no generic version of DIGIFab available.

Is DIGIFab the same as Digibind?

No, DIGIFab is not the same product as Digibind but has demonstrated comparable in vivo binding affinity for digoxin. In a comparative pharmacokinetic study of DIGIFab and Digibind administered in healthy volunteers, DIGIFab rapidly reduced serum free digoxin to undetectable levels within 30 minutes, and serum digoxin levels were reduced to undetectable levels in all subjects.4

Are there other causes of cardiac glycoside toxicity?

In addition to digoxin, other cardiac glycosides exist and have been associated with toxicity or poisoning, including the xenobiotics ouabain and lanatoside C; various plants, including foxglove, dogbane, red squill, lily of the valley, oleander, and henbane; and bufadienolides, cardioactive steroids found in the skin of toads belonging to the family Bufonidae. DIGIFab is not indicated to treat these other forms of cardiac glycoside toxicity.5

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References

  1. DIGIFab Digoxin Immune Fab (ovine) [package insert]. West Conshohocken, PA: BTG International Inc.; 2017.
  2. Reithofer M, Jahn-Schmid B. Allergens with protease activity from house dust mites. Int J Molec Sci. 2017;18(7):1368.
  3. Vandenplas O, Vandezande LM, Halloy JL, Delwiche JP, Jamart J, Looze Y. Association between natural rubber latex and papain. J Allergy Clin Immunol. 1996;97(6):1421-1424.
  4. Ward SB, Sjostrom L, Ujhelyi MR. Comparison of the pharmacokinetics and in vivo bioaffinity of DigiTAb versus Digibind. Ther Drug Monit. 2000;22(5):599-607.
  5. Levine MD, O’Connor A. Digitalis (cardiac glycoside) poisoning. UpToDate. Updated January 2020. https://www.uptodate.com/contents/digitalis-cardiac-glycoside-poisoning. Accessed October 2, 2020
  6. Dart RC, Goldfrank LR, Erstad BL, et al. Expert consensus guidelines for stocking of antidotes in hospitals that provide emergency care. Ann Emerg Med. 2018;71(3):314-325.

INDICATIONS AND USAGE

DIGIFab is indicated for the treatment of patients with life-threatening or potentially life-threatening digoxin toxicity or overdose, including:

  • Known suicidal or accidental consumption of fatal doses of digoxin: 10 mg or more of digoxin in healthy adults, or 4 mg (or more than 0.1 mg/kg) in healthy children, or ingestion of an amount that can cause steady state serum concentrations of ≥10 ng/mL;
  • Chronic ingestions causing steady-state serum digoxin concentrations >6 ng/mL in adults or 4 ng/mL in children;
  • Manifestations of life-threatening toxicity of digoxin overdose such as severe ventricular arrhythmias, progressive bradycardia, and second or third degree heart block not responsive to atropine, serum potassium levels exceeding 5.5 mEq/L in adults or 6 mEq/L in children with rapidly progressive signs and symptoms of digoxin toxicity.

IMPORTANT SAFETY INFORMATION

Warnings and Precautions

General

Suicidal ingestion may result from more than one drug. Consider toxic effects of other drugs or poisons in cases where signs and symptoms of digitalis toxicity are not relieved by administration of DIGIFab.

Rapid drop in serum potassium concentration may occur after treatment. Monitor frequently.

Patients with poor cardiac function may deteriorate secondary to the withdrawal of the inotropic action of digoxin by DIGIFab. Monitor frequently and provide additional inotropic support if needed. Postpone re-digitalization, if possible, until the Fab fragments have been eliminated; this may require several days or a week or longer in patients with impaired renal function.

Hypersensitivity Reactions

Anaphylaxis and hypersensitivity reactions are possible. Carefully monitor patients for signs and symptoms of an acute allergic reaction and if one occurs, stop the infusion and treat immediately with appropriate emergency medical care.

Patients with known allergies to sheep protein or those who have previously received intact ovine antibodies or Fab are particularly at risk for an anaphylactic reaction.

Do not administer DIGIFab to patients with a known history of hypersensitivity to papaya or papain unless the benefits outweigh the risks and appropriate management for anaphylactic reactions is readily available.

Use of DIGIFab in Renal Failure

The elimination half-life of DIGIFab in renal failure has not been clearly defined. Monitor patients with severe renal failure who receive DIGIFab for a prolonged period for possible recurrence of toxicity. Monitoring of free (unbound) digoxin concentrations after the administration may be appropriate.

Laboratory Tests

DIGIFab may interfere with digitalis immunoassay measurements. Thus, standard serum digoxin concentration measurements may be clinically misleading until the Fab fragments are eliminated from the body. This may take several days or a week or more in patients with markedly impaired renal function. If possible, obtain serum digoxin samples before DIGIFab administration to establish the level of serum digoxin at the time of diagnosis.

The total serum digoxin concentration may rise precipitously following administration of DIGIFab, but this will be almost entirely bound to the Fab fragment and not able to react with receptors in the body.

Adverse Reactions

The most common adverse reactions (>7%) related to DIGIFab administration are worsening congestive heart failure (13%), hypokalemia (13%) and worsening atrial fibrillation (7%).

Please see full Prescribing Information.