Digoxin Immune Fab

Brand names DigiFab

Medication error Look-alike, sound-alike drug names. Digoxin immune fab may be confused with digoxin.(1) potential

Contraindications Contraindications: None and warnings Warnings: Hypersensitivity to digoxin immune Fab (DigiFab), sheep products, or any component of the formulation.(2) Patients allergic to papain, chymopapain, or papaya extracts may be allergic to DigiFab.(2) Likewise, those with known allergies to dust mites and latex may experience a cross-allergy.(16) If digoxin has been used to treat heart failure, exacerbation of symptoms of heart failure may appear as serum digoxin concen- trations fall.(2) (See the Comments section.) Use cautiously in those with hypokalemia, poor heart function (withdrawal of inotropic effect), and/or renal failure.(2) Rapid drop in serum potassium may occur after treatment with Fab; therefore, monitor potassium for the first several hours after Fab administration.(2)

Infusion-related Monitor for signs and symptoms of an acute allergic reaction (e.g., urticaria, pruritus, cautions erythema, angioedema, bronchospasm with wheezing or cough, stridor, laryngeal edema, hypotension, tachycardia) and treat immediately with appropriate emergency medical care (e.g., oxygen, diphenhydramine, corticosteroids, volume expansion and airway management). If anaphylactoid, reaction occurs discontinue the DigiFab and administer epinephrine.(2-4) Because skin testing has not proved useful in predicting allergic response to Digibind and because it may delay urgently needed therapy, skin testing was not performed during the clinical studies of DigiFab and is not suggested prior to dosing with this product. Individuals at high risk for allergy should receive a test dose.(17) Give a 1:100 dilution by mixing 0.1 mL of reconstituted Fab (9.5 mg/mL) in 9.9 mL NS (95 mcg/mL). Inject 0.1 mL of the dilution through 0.22-micron filter intradermally or place one drop on skin and make a ¼ scratch through drop with a sterile needle.(17) Evaluate test site for 20–30 minutes.(17)

Dosage For manifestations of severe, life-threatening or potentially life-threatening, digitalis toxicity unresponsive to other therapies.(2,4) Dose should be based on (1) the estimated amount of digoxin or digitoxin ingested, or (2) measured serum digoxin concentration.(2) If the dose estimated based on ingested amount differs substantially from that calculated based on the serum digoxin, the larger dose estimate should be used.(2) 40 mg of purified DigiFab (one vial) binds 0.5 mg of digoxin or digitoxin.(2) Summary of general DigiFab dosing guidelines:

Signs and Symptoms of Digoxin Toxicity Acute Ingestion Unknown amount of digoxin, Total of 20 vials of DigiFab. Administration of 10 vials including inability to estimate initially may decrease febrile reaction. If required, amount, and no serum digoxin administer another 10 vials. If patients in <20 kg, concentration available monitor for volume overload. Known amount of digoxin* DigFab dose (vials) = amount of digoxin ingested (mg)/0.5 mg per vial Chronic Ingestion No serum digoxin <20 kg: administer 1 vial DigiFab concentration available ≥20 kg: administer 6 vials of DigiFab Serum digoxin concentration DigiFab dose (vials) = [(serum digoxin concentration available [ng/mL] × weight [kg])/100] *If the patient ingested digoxin tablet, the total body load will approximate the amount ingested (in mg) multiplied by the bioavailability (0.8) of the tablet formulation.  296 Digoxin Immune Fab

Dosage (cont.) Clinical improvement in signs and symptoms of digitalis toxicity generally occur in ≤30 minutes following administration of DigiFab.(2) Complete reversal of cardiac and noncardiac manifestations generally occur 3–4 hours after completion of the infusion.(11) If toxicity has not adequately reversed after several hours, or appears to recur, administer DigiFab at a dose guided by clinical judgment. The diagnosis of digitalis toxicity should be questioned if the patient fails to respond to an adequate dose of DigiFab. DigiFab dosing estimate based on patient weight and measure serum digoxin concentration:

Serum Digoxin Concentration (ng/mL) Weight (kg) 1 2 4 8 12 16 20 1 0.4 mg* 1 mg* 1.5 mg* 3 mg 5 mg 6.5 mg 8 mg 3 1 mg* 2.5 mg* 5 mg 10 mg 14 mg 19 mg 24 mg 5 2 mg* 4 mg 8 mg 16 mg 24 mg 32 mg 40 mg 10 4 mg 8 mg 16 mg 32 mg 48 mg 64 mg 80 mg 20 8 mg 16 mg 32 mg 64 mg 96 mg 128 mg 160 mg 40 0.5 vial 1 vial 2 vials 3 vials 5 vials 7 vials 8 vials 60 0.5 vial 1 vial 3 vials 5 vials 7 vials 10 vials 12 vials 70 1 vial 2 vials 3 vials 6 vials 9 vials 11 vials 14 vials 80 1 vial 2 vials 3 vials 7 vials 10 vials 13 vials 16 vials 100 1 vial 2 vials 4 vials 8 vials 12 vials 16 vials 20 vials *Dilute reconstituted vial with 36 mL isotonic sterile saline (final concentration of 1 mg/mL) may be desirable.

Chronic toxicity and SDC unavailable: Infants and children ≤20 kg, one vial (40 mg) is adequate to reverse most cases of toxicity. If ≥20 kg, give 6 vials (240 mg).(6)

Dosage adjustment Fab fragments may be eliminated more slowly in patients with renal failure.(2,4) in organ dysfunction

Maximum dosage Not established. Following acute ingestion, 760 mg should be sufficient. For chronic ingestion, a single vial (40 mg) should be sufficient for infants and small children (<20 kg) and 240 mg (6 vials) should be sufficient for children ≥20 kg and adults.(6)

Additives Processed with papain, which may cause hypersensitivity reactions in patients allergic to papaya, other papaya extracts, papain, chymopapain, or the pineapple enzyme bromelain.(2)

Suitable diluents SWI, NS(2)

Maximum 10 mg/mL(2) concentration

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