Page 190 - product-manual

TM/MC TM/MC
PHARMACOLOGICAL ACTIVITIES - TOXICOLOGY - DRUG INTERACTIONS

Thiamine Hydrochloride [Vitamin B ] (C H ClN OS.HCl)
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Thiamine (vitamin B ) is an essential cofactor in the decarboxylation of pyruvate and alpha-
1
ketoglutarate and these reactions are essential for aerobic metabolism. Deficiency of thiamine
blocks CNS aerobic metabolic pathways. In cats, initial thiamine deficiency can develop into
central vestibular disease, head tremor, mydriasis, and cervical ventroflexion, which may
progress to opisthotonos, coma, and death. In dogs, ataxia, paresis, vestibular signs, and seizures
have been observed (Ettinger & Feldman, 2000a).

Cats are more susceptible to thiamine deficiency than dogs as they require about four times as
much thiamine in the diet. Fish-based diets that contain active thiaminases before processing can
destroy thiamine added to these diets and in the heat processing of dog and cat foods, large losses
of thiamine can occur. Canned foods often contain gelling agents that increase the pH of the
food and in combination with prolonged heat during retorting results in extensive inactivation
of thiamine. Moreover, sulphites used for food preservation, cleave the thiamine molecule at the
methylene bridge making thiamine inactive. Thiamine deficiency associated with the feeding of
meat preserved with sulphur dioxide has been reported in cats and dogs (NRC, 2006).

TOXICOLOGY Toxicity for vitamin B has not been documented in dogs and cats when administered orally in therapeutic doses.
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Intravenous LD of vitamin B is 50-125 mg/kg of body weight in dogs (NRC, 1987).
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50

DRUG Validated interactions studies do not exist for thiamine preparations. However, laboratory
INTERACTIONS studies suggest that digoxin may reduce the ability of heart cells to absorb and utilize
thiamine. Diuretics such as furosemide may reduce the levels of thiamine in the body
(UMMC, 2012b).

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