Forms of Oral Cobalamin

[helvella]

Well aware that this doesn't really apply to Pernicious Anaemia, but where else to ask?

NICE BNF refers to Hydroxocobalamin for injections (as well as one Cyanocobalamin product). But the only oral form they mention is Cyanocobalamin. No mention is made of Methylcobalamin.

And when I search for commercially available products I find a reasonable number of Cyanocobalamins, loads and loads of Methylcobalamins, and a small number of Hydroxocobalamins.

Why so few Hydroxocobalamin tablets/lozenges/etc.? Do the advantages of Hydroxocobalamin when injected not apply at all to oral forms?

[Gambit62 Administrator]

don't know but I suspect there are two things going on

a) cyanocobalamin is more stable than hydroxo so is cheaper so if you are looking at the cheap end of the market it's going to be a happier fit. There is only one area I am aware of where cyano is contraindicated - in any form and that is a rare genetic condition called lebers syndrome which affects men more than women. The advantage of hydroxo over cyano is that on average it is retained longer, at least in injected form. The fact that very relatively little of oral gets into blood stream, compared to injections, means that that advantage is marginal so unless you have lebers cyano has the edge for tablets.

b) at the other end of the spectrum is methyl which is pushed as being more natural (it isn't) so taping into different markets where selling through urban myths about being better absorbed seem to work. More expensive - so bigger profits if you are working on a margin basis.

I have no idea about the relative stability of methyl and cyano in tablet form - could be significantly different from stability in liquid form.

[helvella in reply to Gambit62]

Thank you.

Yes, methyl does seem to be pushed. A lot.

One reason I have been wondering about this is based on the use of hydroxocobalamin for cyanide poisoning. Is it possible that in addition to its function as a source of B12, hydroxocobalamin - even in tablet form - helps to bind to something (whether cyanide-based or otherwise) and remove it from the body?

[Gambit62 Administrator in reply to helvella]

I don't think the biochemistry/genetics of why on average hydroxo is retained longer is known- in studies there are signficant numbers of individuals who retain cyano longer than hydroxo.

hydroxo is used to treat cyanide poisoning because cobalamin actually likes being bound to the cyano complex more than it likes to be bound to the hydroxo complex with the result that the cyano complex is no longer available to react to other chemicals in the body causing harm and the hydroxo complex appears to have no harmful effects.