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Patients undergoing digoxin therapy who exhibit risk factors for digoxin toxicity should be closely monitored so that any signs of poisoning are identified early to ensure timely treatment.1
Risk factors for potentially life-threatening digoxin toxicity
Decreased Renal Function1,4
Renal impairment can lead to increased digoxin levels, as digoxin is primarily eliminated by the kidneys1-4
Multiple Concomitant Medications4
Many medications can cause pharmacokinetic and pharmacodynamic interactions with digoxin or a decrease in renal function4
Advanced Age and Medical Illness3-6
Older patients are more likely to have decreased renal function and to be taking potentially interacting concomitant medications3-5; advanced heart failure is also associated with decreased renal function6
Certain electrolyte imbalances (eg, hypokalaemia, hypercalcemia, hypomagnesemia) can increase sensitivity to digoxin effects1,2,*
*In patients with toxicity from acute ingestion, hyperkalaemia is associated with high mortality2
Fluid loss or poor fluid intake can lead to electrolyte imbalance1,4
Any ONE should raise clinical suspicion for POTENTIALLY LIFE-THREATENING DIGOXIN TOXICITY
For potentially life-threatening digoxin toxicity, think R.A.P.I.D.1-3
McAlister FA, Ezekowitz A, Tonelli M, Armstrong PW. Renal insufficiency and heart failure: Prognostic and therapeutic implications from a prospective cohort study. Circulation. 2004;109(8):1004-1009.
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.
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.
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
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.
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.
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.
The most common adverse reactions (>7%) related to DIGIFab administration are worsening congestive heart failure (13%), hypokalemia (13%) and worsening atrial fibrillation (7%).