Hydroxocobalamin

Category: vitamin

Aliases: OH-Cbl, Hydroxycobalamin, Vitamin B12a, Cyanokit

Pharmacological Mechanism

Cobalamin with a hydroxyl ligand at the central cobalt. Binds transcobalamin II more tightly than cyanocobalamin, giving a substantially longer plasma residence time (effective t½ weeks to months after IM). Converted intracellularly to methylcobalamin and adenosylcobalamin via the canonical MMACHC/MMADHC trafficking pathway. Also acts as a potent cyanide chelator — forms cyanocobalamin which is renally excreted, hence its Rx role (Cyanokit) in smoke-inhalation poisoning.

Half-Life (t½)

IM: 26.2h, IV: 26.2h

Dosing Guidelines

• IM: Typical 1000 mcg (Range: 1000–1000 mcg)
• IV: Typical 1000 mcg (Range: 1000–1000 mcg)
• PO: Typical 1000 mcg (Range: 1000–1000 mcg)

Target Organ Systems

• nervous
• immune-hematologic

Interactions

• Cyanocobalamin (synergistic): Same family; OH-Cbl is the preferred parenteral form — longer t½, tighter TCII binding, no cyanide ligand.
• Methylcobalamin (synergistic): Hydroxocobalamin is converted intracellularly to methylcobalamin + adenosylcobalamin.

Pathways It Modulates

• Vitamin B12 (cobalamin) metabolism (substrate) — B12 (hydroxy form)

Chemical Identifiers

• PubChem CID: 44475014
• Formula: C62H89CoN13O15P
• Molecular weight: 1346.37 g/mol
• InChIKey: YOZNUFWCRFCGIH-WZHZPDAFSA-K
• SMILES: CC1=CC2=C(C=C1C)N(C=N2)[C@@H]3[C@@H]([C@@H]([C@H](O3)CO)OP(=O)([O-])O[C@H](C)CNC(=O)CC[C@@]\4([C@H]([C@@H]5[C@]6([C@@]([C@@H](C(=N6)/C(=C\7/[C@@]([C@@H](C(=N7)/C=C\8/C([C@@H](C(=N8)/C(=C4\[N-]5)/C)CCC(=O)N)(C)C)CCC(=O)N)(C)CC(=O)N)/C)CCC(=O)N)(C)CC(=O)N)C)CC(=O)N)C)O.[OH-].[Co+3]

References

• PMID 25117994