Vitamin B12 There is four types of parenteral Vitamin B12 available: Cyanocobalamin 100 mcg/ml and 1000 mcg/ml best used as IM to prevent rapid loss via kidneys Hydroxycobalamin IM (compounded 1000 mcg/ml or more) known as long acting B12 (binds better to plasma proteins than cyanocobalamin) Methylcobalamin IV (compounded 1000 mcg or more up to 5000 mcg/ml) Adenosylcobalamin IV Common dose is 1000 mcg IM or IV Vitamin B12 as hydroxycobalamin is synthesized exclusively by microorganisms and is found in the liver of animals bound to protein as methylcobalamin = metabolically active form of Vitamin B12 Hydroxycobalamin is a chelator of cyanide and is used in cyanide poisoning Hydroxocobalamin is most generally used for vitamin B12 replacement therapy and is considered the drug of choice for vitamin B12 deficiency by the Martindale Extra Pharmacopoeia (Sweetman, 2002) and the World Health Organization (WHO) Model List of Essential Drugs

It qualifies as a conditionally essential amino due to the bodys ability to burn through L-Carnitine faster than it can produce it, requiring many to have to increase their dietary intake or supplement itespecially in older age when L-Carnitine production decreases
Cegla J, Troke RC, Jones B, Tharakan G, Kenkre J, McCullough KA, et al
10.1016/j.jtbi.2003.08.001
Pairing them allows the GHRH-R signal to remain elevated while the GHS-R1a pulse is delivered on the researcher's schedule rather than on the model's circadian ghrelin rhythm
Tynes, T., Hannevik, M., Andersen, A., Vistnes, A