Digoxin Immune Fab precautions
| Digoxin Immune Fab |
|---|
| DIGIFAB® FDA Package Insert |
| Indications and Usage |
| Dosage and Administration |
| Contraindications |
| Warnings |
| Precautions |
| Adverse Reactions |
| Drug Interactions |
| Use in Specific Populations |
| Overdosage |
| Description |
| Clinical Pharmacology |
| Nonclinical Toxicology |
| How Supplied/Storage and Handling |
| Patient Counseling Information |
| Labels and Packages |
| Clinical Trials on Digoxin Immune Fab |
| ClinicalTrials.gov |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Abdurahman Khalil, M.D. [2]
For patient information about Digoxin immune fab, click here.
PRECAUTIONS
General:
Standard management of digitalis intoxication includes withdrawal of the intoxicating agent, correction of electrolyte disturbances (especially hyperkalemia), acid-base imbalances, hypoxia and treatment of cardiac arrhythmias.
Massive digitalis intoxication can cause hyperkalemia; administration of potassium supplements in the setting of digitalis intoxication may be hazardous. After treatment with DigiFab, the serum potassium concentration may drop rapidly and must be monitored frequently, especially after the first several hours after DigiFab is given (see Laboratory Tests).
Patients with poor cardiac function may deteriorate secondary to the withdrawal of the inotropic action of digoxin by DigiFab. If needed, additional support can be provided by using other intravenous inotropes such as dopamine, dobutamine or vasodilators. However, care must be taken not to aggravate the digitalis induced rhythm disturbances. Re-digitalization should be postponed, if possible, until the Fab fragments have been eliminated from the body, which may require several days, and patients with impaired renal function may require a week or longer.
Use of DigiFab in Renal Failure:
The elimination half-life of DigiFab in renal failure has not been clearly defined, although patients with renal dysfunction have been successfully treated with Digibind.3,12 There is no evidence to suggest that the time-course of therapeutic effect is any different in these patients than in patients with normal renal function, but excretion of the Fab fragment-digoxin complex from the body is probably delayed. There is one case report of recurrence of atrioventricular block due to digoxin in a functionally anephric patient 10 days after its initial reversal by ovine Fab therapy.12 This clinical event persisted for more than a week. In patients that are functionally anephric, failure to clear the Fab-digoxin complex from the blood by glomerular filtration and renal excretion may be anticipated. It is uncertain whether the failure to eliminate the Fab-digoxin complex in severe renal impairment may lead to re-intoxication with digoxin following the release of previously bound digoxin into the blood. However, patients with severe renal failure who receive DigiFab for digitalis toxicity should be monitored for a prolonged period for possible recurrence of toxicity. Monitoring of free (unbound) digoxin concentrations after the administration may be appropriate in order to establish recrudescent toxicity in renal failure patients.13
Formation of Antibodies to DigiFab:
Prior treatment with digoxin-specific ovine immune Fab carries a theoretical risk of sensitization to ovine serum protein (see WARNINGS) and possible diminution of the efficacy of the drug due to the presence of human antibodies against ovine Fab. Human antibodies to ovine Fab have been reported in some patients receiving Digibind, however, to date, there have been no clinical reports of human anti-ovine immunoglobulin antibodies causing a reduction in binding of ovine digoxin immune Fab or neutralization response to ovine digoxin immune Fab.
Laboratory Tests:
DigiFab will interfere with digitalis immunoassay measurements in the same way that has been reported for Digibind.14,15 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. Therefore, serum samples for digoxin concentration should be obtained before DigiFab administration, if at all possible. Such measurements would establish the level of serum digoxin at the time of diagnosis of digitalis intoxication. At least 6 to 8 hours are required for equilibration of digoxin between serum and tissue, so absorption of the last dose may continue from the intestine. Therefore, serum measurements may be difficult to interpret if samples are drawn soon after the last digitalis dose. Patients should be closely monitored, including temperature, blood pressure, electrocardiogram, and potassium concentration, during and after administration of DigiFab. The total serum digoxin concentration may rise precipitously following administration of DigiFab, but this will be almost entirely bound to the Fab fragment and therefore not able to react with receptors in the body.
Digoxin causes a shift of potassium from inside to outside the cell, such that severe intoxication can cause a life-threatening elevation of serum potassium. This may lead to increased urinary excretion of potassium so that a patient may have hyperkalemia but a whole body deficit of potassium. When the toxic effects of digoxin are reversed by DigiFab, potassium shifts back into the cell with a resulting decline in serum potassium concentration. This hypokalemia may develop rapidly. For these reasons, serum potassium concentration should be followed closely, especially during the first several hours after DigiFab administration. Cautious potassium supplementation should then be given when necessary.
Information for Patients:
Patients should be advised to contact their physician immediately if they experience any signs and symptoms of delayed allergic reactions or serum sickness (e.g., rash, pruritus, urticaria) after hospital discharge.
References
http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=6832767f-db6b-4eea-b88b-bdfc905749e1