Elephant specific information, if available, is in blue.

Chemistry – A water-soluble B-complex vitamin, thiamine HCl occurs as bitter-tasting, white, small hygroscopic crystals, or crystalline powder that has a characteristic yeast-like odor. Thiamine HCl is freely soluble in water and slightly soluble in alcohol and has pKas of 4.8 & 9.0. The commercially available injection has a pH of 2.5-4.5. Thiamine HCl may also be known as Aneurine HCl , Thiamin HCl , Thiamine Chloride , Thiaminium Chloride Hydrochloride , or Vitamin B1 .

 

Storage/Stability/Compatibility – Thiamine HCl for injection should be protected from light and stored at temperatures less than 40°C and preferably between 15-30°C; avoid freezing.

 

Thiamine HCl is unstable in alkaline or neutral solutions or with oxidizing or reducing agents. It is most stable at a pH of 2.

 

Thiamine HCl is reportedly compatible with all commonly used intravenous replacement fluids. Compatibility is dependent upon factors such as pH, concentration, temperature and diluents used. It is suggested to consult specialized references for more specific informa­tion (e.g., Handbook on Injectable Drugs by Trissel; see bibliography).

 

Pharmacology – Thiamine combines with adenosine triphosphate (ATP) to form a com­pound (thiamine diphosphate/thiamine pyrophosphate) that is employed for carbohydrate metabolism, but does not effect blood glucose concentrations.

 

Absence of thiamine results in decreased transketolase activity in red blood cells and in­creased pyruvic acid blood concentrations. Without thiamine triphosphate, pyruvic acid is not converted into acetyl-CoA, diminished NADH results with anaerobic glycolysis pro­ducing lactic acid. Lactic acid production is further increased secondary to pyruvic acid conversion. Lactic acidosis may occur.

 

Uses/Indications – Thiamine is indicated in the treatment or prevention of thiamine defi­ciency states. Symptoms of thiamine deficiency may be manifested as gastrointestinal (anorexia, salivation), neuromuscular/CNS signs (ataxia, seizures, loss of reflexes), or car­diac effects (brady- or tachyarrhythmias). Deficiency states may be secondary to either a lack of thiamine in the diet or the presence of thiamine destroying compounds in the diet (e.g., bracken fern, raw fish, amprolium, thiaminase-producing bacteria in ruminants).

 

Thiamine has also been used in the adjunctive treatment of lead poisoning and ethylene glycol toxicity (to facilitate the conversion of glyoxylate to nontoxic metabolites).

 

Pharmacokinetics – Thiamine is absorbed from the GI tract and is metabolized by the liver. Elimination is renal, the majority being metabolites.

 

Contraindications/Precautions/Reproductive Safety – Thiamine injection is contraindi­cated in animals hypersensitive to it or any component of it.

 

Adverse Effects/Warnings – Hypersensitivity reactions have occurred after injecting this agent. Some tenderness or muscle soreness may result after IM injection.

 

Overdosage/Acute Toxicity – Very large doses of thiamine in laboratory animals have been associated with neuromuscular or ganglionic blockade, but the clinical significance is unknown. Hypotension and respiratory depression may also occur with massive doses. A lethal dose of 350 mg/kg has been reported. Generally, no treatment should be required with most overdoses.

 

Drug Interactions – Thiamine may enhance the activity of neuromuscular blocking agents; clinical significance is unknown.

 

Drug/Laboratory Interactions – Thiamine may cause false-positive serum uric acid re­sults when using the phosphotungstate method of determination or urobilinogen urine spot tests using Ehrlich’s reagent. The Schack and Wexler method of determining theo­phylline concentrations may be interfered with by large doses of thiamine.

 

Doses –

Horses:

For thiamine deficiency:

a)   0.5 – 5 mg/kg IV, IM or PO (Robinson 1987)

b)   100 – 1000 mg IM, SQ, or IV (depending on formulation). (Phillips 1988b)

 

 

Monitoring Parameters –

1)   Efficacy

 

Client Information – Epidemiologic investigation as to the cause of thiamine deficiency (diet, plants, raw fish, etc.) should be performed with necessary changes made to prevent recurrence.

 

Dosage Forms/Preparations/FDA Approval Status/Withholding Times –

 

Veterinary-Approved Products:

Thiamine HCl for Injection 200 mg/ml and 500 mg/ml in 30 and 100 ml vials

Available generically labeled; (Rx) Labeled for use in small and large animals. Approval status is uncertain.

 

There are several B-complex vitamin preparations available that may also have thiamine included.

 

Human-Approved Products:

Thiamine Oral Tablets  50 mg, 100 mg, 250 mg, & 500 mg; Available generically la­beled; (OTC)

Thiamine Enteric Coated Tablets 20 mg; Thiamilate® (Tyson) (OTC)

 

Thiamine HCl for Injection  100 mg/ml in 1, 2, 10 and 30 ml vials & 1 ml amps; Available generically labeled; (Rx)