Hydroxycobalamin is an unique form of vitamin B12, it is more readily converted into the coenzyme ( factor needed for the effective functioning of one of the body’s vital enzymes)  forms than conventional cyanocobalamin. Many vitamins, including B12, are not biologically active in the form in which they are normally found in food, but are instead used by the body as part of a coenzyme. In other words, in these cases, the body has to convert a vitamin into its coenzyme form in order for the vitamin to exert its biological function.

Or, in the case of vitamin B12: not function, but functions. The body uses vitamin B12 in the form of two different coenzymes, each of which plays a different role in the body. Adenosylcobalamin [also known as cobamamide or dibencozide], was discovered earlier, and is the better-known of these coenzymes. Methylcobalamin is the other coenzyme form of B12. Methylcobalamin prevents the creeping numbness, dementia, and spongy degeneration of the nerve cells (neurons) seen in B12 deficiency. Adenosylcobalamin helps the body to process some amino acids, and to form substances used in the body’s energy cycle. One coenzyme can’t substitute for the other, any more than you can use your house keys to start your car.

A good diet and supplement program usually provides the body with a generous supply of adenosylcobalamin, Methylcobalamin is different. While adenosylcobalamin is readily stored up in the liver (and, to a lesser extent, the kidneys and other tissues), methylcobalamin’s function requires that it be freely circulate in body fluids like cytosol (the liquid medium of the cell), plasma, and the fluid that bathes the brain and spinal cord (cerebrospinal fluid). Because of this, Methylcobalamin doesn’t stay in the body for very long.

Thus, while a person getting enough of the basic vitamin (cobalamin) will always have plenty of adenosylcobalamin, there is no special store of protective Methylcobalamin  in the nervous system.  The body’s Methylcobalamin reserves can easily be brought below optimal levels, and those reserves are quickly depleted and must be constantly replenished.

A regular B12 (cyanocobalamin) supplement, the body must first convert its B12 into Hydroxycobalamin order to form the B12 coenzymes. This involves the removal and detoxification of the cyanide molecule, followed by biochemical reduction to a less oxidized (+1 valence) state, and then the enzymatic conversion of the reduced cobalamin into one of two metabolically active coenzyme forms. By taking a preformed Hydroxycobalamin supplement, you can skip over this first biochemical stumbling block, allowing for unhampered formation of adenosylcobalamin and Methylcobalamin.


Methylcobalamin or Hydroxycobalamin?

Because the body can interconvert the two B12 coenzymes, and because the body stores adenosylcobalamin but not Methylcobalamin, an adequate supply of Methylcobalamin usually ensures that you’ll have plenty of adenosylcobalamin, too – but not vice-versa. Because of this fact, and because of the powerful neuroprotective effects of Methylcobalamin, a fully-formed Methylcobalamin supplement is the best choice for most people.

Exceptions are persons with known or suspected cyanide toxicity, where Hydroxycobalamin has an unique role to play. Hydroxycobalamin helps the body to rid itself of cyanide, both by reacting with the toxin to an excretable form cyanocobalamin and by enhancing the detoxification of cyanide through its conversion into the less toxic thiocyanate. In isolated human cells, Hydroxycobalamin penetrates cyanide-laden cells and detoxifies the toxin directly.  Also, at lower doses, oral Hydroxycobalamin increases the urinary excretion of thiocyanate in laboratory animals fed cyanide-containing diets.

Sublingual Hydroxycobalamin, complexed with beta-cyclodextrin, is an ideal choice for a B12 supplement in persons concerned with chronic, low-level cyanide toxicity.

 

References used for the original article include:

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Forsyth JC, Mueller PD, Becker CE, Osterloh J, Benowitz NL, Rumack BH, Hall AH. Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers. J Toxicol Clin Toxicol. 1993; 31(2): 277-94.

Sauer SW, Keim ME. Hydroxocobalamin: improved public health readiness for cyanide disasters. Ann Emerg Med. 2001 Jun; 37(6): 635-41.

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Smith AD, Duckett S. Cyanide, vitamin B-12, experimental demyelination and tobacco amblyopia. Br J Exp Pathol. 1965 Dec; 46(6): 615-22.

Mushett C, Kelley K, Boxer G, Rickards J. Antidotal Efficacy of Vitamin B12a (Hydroxo-Cobalamin) in Experimental Cyanide Poisoning. Proc Soc Exp Biol Med. 1952 Oct; 81(1): 234-7.