Hydroxocobalamin and Cyanocobalamin in Addisonian Anæmia

Efficacy of intramuscular hydroxocobalamin supplementation in cats with cobalamin deficiency and gastrointestinal disease

“…Further dialysis experiments showed that OH‐Cbl passed more slowly through membranes than does CN‐Cbl, and that OH‐Cbl is bound to serum proteins in far greater quantities than is CN‐Cbl 15 . These observations were confirmed in long‐term studies when humans with pernicious anemia were given equal amounts of either OH‐Cbl or CN‐Cbl IM injections, 14,17 and similar results have been published when comparing oral OH‐Cbl to CN‐Cbl 29 . Against this background, it is interesting to note that it has also been mentioned in small animal medicine that CN‐Cbl might fail to increase serum Cbl concentrations for reasons currently not understood, and it has been speculated that OH‐Cbl might instead be more effective in these patients 11 …”

“…Superior bioavailability of OH‐Cbl over CN‐Cbl has also been proven in humans. Slower disappearance of OH‐Cbl from site of injection, increased liver uptake, and less rapid urinary excretion when compared with CN‐Cbl were demonstrated by various authors 14,15‐20,28 . Hertz et al reported that after IM injection of 1 mg CN‐Cbl and OH‐Cbl, healthy individuals excreted within 24 hours about 80% and about 25%, respectively, in the urine 15 .…”

“…When the same dogs received OH‐Cbl, higher serum binding and more prolonged increases in serum Cbl concentrations and lower urinary excretion was noted compared with CN‐Cbl 18 . It was speculated that the difference in serum binding may lie in the chemical stability of CN‐Cbl, which limits the sites at which it may be bound as compared to OH‐Cbl which readily dissociated and may equilibrate with a variety of serum constituents 17 . Possible differences in protein binding likely have also implications for cellular markers of Cbl availability as only Cbl bound to transcobalamin is available to cells 30 …”

“…In cats, only the use of CN‐Cbl has been investigated so far, 4,7,8 and it was recently shown that a Cbl supplementation scheme consisting of 6 weekly IM (250 μg) injections of CN‐Cbl failed to fully normalize serum and urine MMA concentrations in hypocobalaminemic cats with enteropathy 7 . In people with various types of Cbl deficiencies, the natural‐occurring OH‐Cbl is considered the mainstay treatment and numerous studies consistently showed superior tissue retention rates of Cbl after supplementation with OH‐Cbl rather than CN‐Cbl together with increased urinary excretion of CN‐Cbl 12‐20 . In addition, IM injections of OH‐Cbl are thought to cause less pain than CN‐Cbl in people 15 …”

Maintenance Therapy of Pernicious Anaemia

“…They all found much higher levels both initially and after several weeks when compared with CN B12 in pernicious anaemia patients [2,20,3]. After a single injection of 1 mg of OH B12 normal values of serum Bi2 were observed in several patients for periods of 6 to 13 months.…”