Digoxin Immune Fab
DigiFab · Digibind
Antidote — antidigoxin antibody fragment
Ovine Fab fragments bind free digoxin → the complex is renally excreted → rapidly reverses digoxin/digitoxin toxicity.
Indications
- •Life-threatening digoxin toxicity (ventricular arrhythmias, high-grade block, hyperkalemia >5, ingestion of large amount, level >10–15)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Known amount | Vials = (mg ingested × 0.8) / 0.5; or use serum level formula | — |
| Empiric (unknown, acute vs chronic) | Acute: 10–20 vials; chronic: 3–6 vials | — |
Pharmacokinetics
Onset within 30 min; complete effect in hours. Renally excreted.
Side effects
- !Withdrawal of digoxin effect → worsening HF or rapid AF rate
- !Hypokalemia (K⁺ shifts back intracellularly)
- !Rare allergy
Contraindications
- ×None absolute in life-threatening toxicity
Clinical pearls
- ★In dig toxicity with hyperkalemia, give Fab — but be cautious with calcium ('stone heart' concern) and expect K⁺ to fall after reversal.
- ★Total-body digoxin levels become uninterpretable after Fab (measures bound + free).
Other drugs in Others
- Dantrolene
Blocks RYR1 (ryanodine receptor) → ↓ Ca²⁺ release from sarcoplasmic reticulum → muscle relaxation. The only drug for malignant hyperthermia.
- Lipid Emulsion 20%
Theory: 'Lipid sink' sequesters lipophilic drugs (especially LAs), shifts to better Ca²⁺ handling, fatty acid metabolic support.
- Hydroxocobalamin
Vitamin B12a precursor; cyanide binds to cobalt center of hydroxocobalamin → forms cyanocobalamin (B12) → renal excretion. Also scavenges nitric oxide → vasoconstriction.
- Octreotide
Long-acting somatostatin analogue → suppresses splanchnic blood flow, GI/pancreatic secretions, GH, glucagon, insulin, and serotonin/vasoactive-peptide release.
- Alvimopan
Blocks GI mu-opioid receptors WITHOUT crossing the blood-brain barrier → reverses opioid-induced gut slowing while preserving central analgesia. Accelerates return of bowel function.
- Phentolamine
Competitive, reversible α1 + α2 blockade → vasodilation. Short-acting.
- Inhaled Nitric Oxide
Inhaled NO diffuses to pulmonary vascular smooth muscle → ↑ cGMP → SELECTIVE pulmonary vasodilation only in VENTILATED lung units (improves V/Q matching). Inactivated by hemoglobin before reaching systemic circulation → no systemic hypotension.
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert
