Hydroxocobalamin
Cyanokit
Cyanide antidote / NO scavenger
Vitamin B12a precursor; cyanide binds to cobalt center of hydroxocobalamin → forms cyanocobalamin (B12) → renal excretion. Also scavenges nitric oxide → vasoconstriction.
Indications
- •Cyanide toxicity (smoke inhalation from house fires, sodium nitroprusside infusion >2 mcg/kg/min, industrial exposure)
- •Vasoplegic syndrome post-cardiopulmonary bypass (off-label, growing evidence)
- •Distributive shock refractory to vasopressors (off-label)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Cyanide toxicity | 5g IV over 15 min; may repeat 5g once if symptoms persist (max 10g total) | — |
| Vasoplegia (off-label) | 5g IV over 15 min; single dose typically sufficient | — |
| Pediatric cyanide | — | 70 mg/kg IV over 15 min |
Pharmacokinetics
Onset minutes; cyanocobalamin formed within minutes; half-life ~26-31 hr; renal excretion.
Hemodynamic effects
Modest ↑ MAP via NO scavenging — clinically meaningful in vasoplegic states. Less hypotensive than sodium thiosulfate.
Side effects
- !Red/orange discoloration of skin, urine, plasma (lasts 5-35 days)
- !Lab interference (chromogenic assays affected — creatinine, AST, ALT, magnesium falsely altered)
- !Pulse oximetry artifact (falsely low SpO2)
- !Allergic reaction / anaphylaxis (rare)
- !Acute renal injury (oxalate crystals)
- !Hypertension (transient, mild)
Contraindications
- ×Hypersensitivity
Clinical pearls
- ★FIRE VICTIMS with smoke inhalation + altered mental status + lactate >10 mmol/L → empirically give Cyanokit even before lab confirmation. Cyanide tox often coexists with CO toxicity (treat both: 100% O2 ± hyperbaric for CO; hydroxocobalamin for cyanide).
- ★ICE: Cyanokit 5g vial reconstitutes in 200 mL NS → infuse over 15 min via dedicated line.
- ★VASOPLEGIA: when methylene blue contraindicated (G6PD, serotonergic drugs) or has failed, hydroxocobalamin is the next move. Compounded with epinephrine + NE + vasopressin in refractory cases.
- ★Lab artifact for 24-48 hours — communicate with lab + ICU team.
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.
- Octreotide
Long-acting somatostatin analog → 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.
- Digoxin Immune Fab
Ovine Fab fragments bind free digoxin → the complex is renally excreted → rapidly reverses digoxin/digitoxin toxicity.
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert