There are four forms of cobalamin commercially available for injection.
Cynocabalamin which in tests of a non cobalamin deficient human has been tested for retention times. There is no comparative testing of the efficacy of Cynocabalamin versus other forms including no test of the effect on symptoms. No testing of the retention times in a cobalamin deficient body.
Hydroxocobalamin is retained in a non cobalamin human body longer than Cynocabalamin. Conjecture is that this is positive without regards to consideration that the body may use the Cynocabalamin more effectively and therefore is preferable. No testing. That it is "artificial" and therefore may not be as effective is not credible. Conjecture
Methyelcobalamin occurs in the human body and may be more ""bioavialbe" Note: bioavialbe is not a scientific measurement and only means that it is used in a biological process.
Adenosylcobalamin is the redheaded stepchild of forms of cobalamin. It does occur in the human body.
The testing of retention times is a measurement of the total cobalamin in the urine and does not include what the cobalamin is attached to or has been measured in a cobalamin deficient body.
Conclusion the efficacy of the commercial forms of cobalamin or combination of the different forms in the cobalamin deficient body is unknown and not a subject that has been studied.
There are currently 25 known processes in which the human body uses and each of these process if not functioning as intended will cause different issues.
The limitation of 1mg of hydroxocabalamin EOD as being the most robust treatment that is effective is based on "fashion" not science and has been definitively proved to be in error by those on this forum.
That any prodacol that "works" does not equate to the most benificial.
I personally made the error of assuming that more hydroxocabalamin was more effective for me because of the volume. It very well could be it was the frequency that caused the increase in effectiveness.
The most important discovery on this journey was that my peripheral nephropathy was caused by B6 deficency which is rarely diagnosed and often attributed to cobalamin deficiency in error although the pain may be less if treated with B12. I injected B6 at first and now use oral Pyridoxal 5 Phosphate. There is no definitive test for B6 and they only way to find out if the cause of the pain is B6 is to do a trial. I could not think straight in that pain.
Seems to me that the methodology used to measure and evaluate medication is applied to supplementation and is failing to some degree as supplementation is not equivalent to medication.
I am aware that I write from a place where I am not in distress and what I write would have had meaning when I was in the throes of cobalamin deficiency.