Vitamin B12 (cobalamin) is, like methylene blue elsewhere in this catalogue, neither a peptide nor a peptide analog — it is an essential dietary micronutrient with a long-established medical history, well-characterised pharmacology, and a substantial registered-pharmaceutical record for the injectable form. It is one of the few "research" compounds in vendor catalogues that is fully registered, FDA-approved, and routinely prescribed by clinicians for legitimate medical indications. This monograph lays out the chemistry of the injectable forms, the pharmacology, the FDA-approved indications, and the considerations specific to vial-grade cyanocobalamin vs methylcobalamin.
Chemical identity and structure.
Vitamin B12 is a family of cobalt-containing organometallic compounds collectively termed cobalamins. The two forms most commonly sold as injectable research-grade vials are cyanocobalamin (C₆₃H₈₈CoN₁₄O₁₄P, molecular weight 1355.4 g/mol — the cyanide-bound, semi-synthetic stable form) and methylcobalamin (C₆₃H₉₁CoN₁₃O₁₄P, molecular weight 1344.4 g/mol — the biologically active methyl-bound form). Both are deep-red crystalline solids that produce a characteristic red-pink solution in water. The cobalt-corrin ring system at the heart of the molecule is responsible for the colour and the catalytic chemistry.
Mechanism of action.
Cobalamin is an essential cofactor for two mammalian enzymes: methionine synthase (in the cytoplasm, where methylcobalamin participates in the remethylation of homocysteine to methionine) and methylmalonyl-CoA mutase (in the mitochondrion, where adenosylcobalamin catalyses the rearrangement of methylmalonyl-CoA to succinyl-CoA). Deficiency disrupts one-carbon metabolism, leading to megaloblastic anaemia, demyelinating neuropathy, and the characteristic clinical syndrome of cobalamin deficiency. Methylcobalamin and adenosylcobalamin are the active intracellular forms; cyanocobalamin is converted intracellularly to these active forms.
Research applications and the evidence base.
Vitamin B12 has, unusually for this catalogue, a fully registered FDA-approved indication: treatment of cobalamin deficiency, including pernicious anaemia. The published clinical literature includes hundreds of controlled trials in B12 deficiency, neuropathy associated with cobalamin deficit, methylmalonic-acidemia metabolic disorders, and supportive use in malabsorption syndromes. Research applications outside the registered indication include neurology research, one-carbon-metabolism biochemistry, and energy-metabolism studies. Cyanocobalamin and methylcobalamin perform interchangeably in most contexts but differ in pharmacokinetics — methylcobalamin enters intracellular methionine-synthase activity more directly.
Research context.
Vitamin B12 occupies the position of canonical reference cofactor in cobalamin pharmacology and one-carbon-metabolism research. Researchers in cobalamin-deficient model systems use it as the rescue agent; researchers in metabolic biochemistry use it as a defined-cofactor control.
Storage and handling.
Cyanocobalamin and methylcobalamin solutions should be kept refrigerated (2–8 °C) and protected from light — cobalamins are photodegradable, with methylcobalamin notably more light-sensitive than cyanocobalamin. Solutions retain their characteristic red colour when intact; loss of colour indicates degradation and the vial should be discarded.
Quality and COA considerations.
A meaningful COA should confirm identity via absorbance spectroscopy (the characteristic 361 nm peak for cyanocobalamin and 525 nm for methylcobalamin are canonical identity checks), purity by HPLC (≥99% benchmark for pharmaceutical-grade), explicit disambiguation between cyanocobalamin and methylcobalamin (and adenosylcobalamin / hydroxocobalamin if applicable), and sterility and endotoxin testing for any solution intended for injection-model use.
Research-use note: This monograph is an educational summary of the published research literature on injectable Vitamin B12 (cobalamin). The compound has FDA-approved indications for cobalamin deficiency and related conditions; use outside those indications remains research-grade. Nothing here is medical advice or a usage recommendation.