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PHARMACOLOGICAL ACTIVITIES - TOXICOLOGY - DRUG INTERACTIONS

Cyanocobalamin [Vitamin B ] (C H CoN O P)
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Vitamin B has the largest and most complex chemical structure of all the vitamins. It is unique
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among vitamins in that it contains a metal ion, cobalt. In mammals, cobalamin is a cofactor for
only two enzymes, methionine synthase and L-methylmalonyl-CoA mutase (Shils et al., 2006).
A deficiency of cobalamin can cause a clinical and hematologic picture identical to that of folate
deficiency (Ettinger & Feldman, 2000b). There are a number of clinical reports of cobalamin
deficiency in dogs and these reports relate to either deficiencies induced by bacterial overgrowth
of the intestine resulting in decreased availability of cobalamin or genetic abnormalities of
cobalamin metabolism (NRC, 2006).

TOXICOLOGY Toxicity for vitamin B has not been documented in dogs and cats when administered orally in therapeutic
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doses. However, subcutaneous doses of 2 to 33 µg/kg of body weight have been given to dogs, and have
resulted in disturbances of reflex activity (NRC, 2006). Oral LD for cyanocobalamin is 13,500 mg/kg of body
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weight in rats and 22,000 mg/kg of body weight in mice (USP, 2007).

DRUG Medications that reduce levels of vitamin B in the body include proton pump inhibitors such as
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INTERACTIONS esomeprazole, lansprazole, omeprazole and rabeprazole (Kasper, 1999); H blockers including
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cimetidine, famotidine, and ranitidine (Termanini et al., 1998); anti-seizure medications such
as phenytoin, phenobarbital, and primidone; anti-diabetic medication metformin; bile acid
sequestrants including colestipol, cholestyramine, and colsevelam (UMMC, 2012e).

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