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After intravenous injection of Digoxin Immune Fab (Ovine) in the baboon, digoxin-specific Fab fragments are excreted in the urine with a biological half-life of about 9 to 13 hours.1 In humans with normal renal function, the half-life appears to be 15 to 20 hours.2 Experimental studies in animals indicate that these antibody fragments have a large volume of distribution in the extracellular space, unlike whole antibody which distributes in a space only about twice the plasma volume.1 Ordinarily, following administration of DIGIBIND (digoxin immune fab) , improvement in signs and symptoms of digitalis intoxication begins within one-half hour or less.2,3,4,5
The affinity of DIGIBIND (digoxin immune fab) for digoxin is in the range of 109 to 1011 M-1, which is greater than the affinity of digoxin for (sodium, potassium) ATPase, the presumed receptor for its toxic effects. The affinity of DIGIBIND (digoxin immune fab) for digitoxin is about 108 to 109 M-1.
DIGIBIND (digoxin immune fab) binds molecules of digoxin, making them unavailable for binding at their site of action on cells in the body. The Fab fragment-digoxin complex accumulates in the blood, from which it is excreted by the kidney. The net effect is to shift the equilibrium away from binding of digoxin to its receptors in the body, thereby reversing its effects.
1. Smith TW, Lloyd BL, Spicer N, Haber E. Immunogenicity and kinetics of distribution and elimination of sheep digoxin-specific IgG and Fab fragments in the rabbit and baboon. Clin Exp Immunol. 1979; 36:384-396.
2. Smith TW, Haber E, Yeatman L, Butler VP Jr. Reversal of advanced digoxin intoxication with Fab fragments of digoxin-specific antibodies. N Engl J Med. 1976; 294:797-800.
3. Smith TW, Butler VP Jr, Haber E, Fozzard H, Marcus FI, Bremner WF, Schulman IC, Phillips A. Treatment of life-threatening digitalis intoxication with digoxin-specific Fab antibody fragments: Experience in 26 cases. N Engl J Med. 1982; 307:1357-1362.
4. Wenger TL, Butler VP Jr, Haber E, Smith TW. Treatment of 63 severely digitalis-toxic patients with digoxin-specific antibody fragments. J Am Coll Cardiol. 1985; 5:118A-123A.
5. Spiegel A, Marchlinski FE. Time course for reversal of digoxin toxicity with digoxin-specific antibody fragments. Am Heart J. 1985; 109:1397-1399.
Last reviewed on RxList: 10/14/2008
This monograph has been modified to include the generic and brand name in many instances.
Additional Digibind Information
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