Cyanocobalamin (Vitamin B12)

Cyanocobalamin (Vitamin B12) is a water-soluble vitamin essential for normal cellular function, particularly in rapidly dividing cells. - **Primary Use**: Parenteral treatment of Vitamin B12 deficiency. - **Common Causes of Deficiency**: Exocrine pancreatic insufficiency (EPI), inflammatory bowel disease (IBD), and other malabsorptive gastrointestinal diseases. - **Species Specifics**: - **Dogs & Cats**: High prevalence of deficiency secondary to GI/pancreatic disease. Giant Schnauzers (and other breeds like Beagles and Border Collies) may have a genetic defect affecting cobalamin-intrinsic factor complex absorption (Imerslund-Gräsbeck syndrome). - **Ruminants**: Deficiency is often secondary to dietary **cobalt** deficiency, as rumen microflora require cobalt to synthesize B12. > **Clinical Pearl**: Unlike humans, dogs and cats lack the cobalamin-binding protein TC1. This means they can rapidly deplete their B12 stores in just 1-2 months during states of malabsorption, whereas humans take 1-2 years.

กลไกการออกฤทธิ์: Vitamin B12 acts as a crucial coenzyme for two major enzymatic pathways: 1. **Methylmalonyl-CoA mutase**: Converts methylmalonyl-CoA → succinyl-CoA. (Deficiency leads to methylmalonic acidemia/aciduria). 2. **Methionine synthase**: Catalyzes the remethylation of homocysteine → methionine, which is intimately linked with **folate** metabolism. - Required for normal cell growth, nucleoprotein and myelin synthesis, amino acid metabolism, and erythropoiesis. - **Note**: B12 deficiency can cause a functional folate deficiency. Unlike humans, macrocytic anemias do not appear to be a significant component of cobalamin deficiency in dogs or cats.

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