Thiamine

What is thiamine?

Thiamine (Vitamin B1) is an injectable drug and oral vitamin supplement used for the prevention or treatment of thiamine deficiency. Pets may have increased dietary thiamine requirements due to nutritional deficiencies, malnutrition, burns, fever, gastrectomy, chronic hemodialysis, hepatobiliary disease, hyperthyroidism, prolonged infection, intestinal disease, long-term exertion, and prolonged stress. It is used for this purpose in many species, including dogs, cats, horses, cattle, small ruminants, and pigs. 

Thiamine is also used in the treatment of cerebrocortical necrosis in cattle and sheep, in the adjunctive treatment of lead poisoning and ethylene glycol toxicity in cats and dogs, and as adjunctive therapy for seizures in dogs.

Thiamine injectable is only available by prescription from your veterinarian. Several generic veterinary formulations exist, as well as generic human formulations that may be used off-label in animal species. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as their directions may be significantly different from those on the label. 

The U.S. Food and Drug Administration (FDA) does not review non-drug health supplements (e.g., herbals, nutraceuticals, shampoos, and other supplements) for safety or effectiveness before they are sold to the public. Manufacturers of non-drug health supplements must ensure their supplements are safe and labeled accurately. The FDA requires that these non-pharmaceuticals contain a disclaimer that says, “This supplement is not intended to diagnose, treat, cure or prevent any disease.” Health Canada licenses “veterinary health supplements” after reviewing safety, efficacy, and manufacturing information provided by the manufacturer. These supplements are not tested by Health Canada.

Your veterinarian is the best source of information about the safety of non-drug health supplements in pets. Just because a supplement is natural does not mean it is safe. All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses. Supplements can also have side effects, like pharmaceuticals. Few supplements and herbs have been subjected to rigorous scientific trials to determine their efficacy. 

Although the information in this handout may be helpful, it may also be incomplete and may not represent the full range of effects the supplement could have on your pet.

 How do I give my pet thiamine?

• Thiamine injectable is given by either slow intravenous (IV), intramuscular (IM) or subcutaneous (SQ) injection. Pet owners can learn how to give IM or SQ injections at home.
• Thiamine supplement is given orally (by mouth) and comes in many formats, including powder, tablets, elixirs, capsules, and solutions. 
• Give oral supplements with or without food.  
• Follow your veterinarian’s directions and use supplements according to their label.
• Ideally, give this supplement at the same time daily.
• If you are advised to provide these injections at home, follow your veterinarian’s directions carefully. Inappropriate injection and delivery techniques or use of non-sterile materials can result in infections. Dispose of empty medication vials, needles, and syringes in an appropriate container and take them back to your veterinarian for safe disposal.
• Give IV injections slowly and monitor for signs of anaphylaxis (see below).
• Ensure access to fresh, clean drinking water.
• Wash hands after handling
• Do not handle if you have a known sensitivity to this supplement.

Thiamine should take effect within several days, but improvements in clinical signs are not always outwardly noticeable. However, side effects can take effect immediately. 

What if I miss giving my pet the supplement?

If you miss a dose, give it as soon as you remember. However, if it is almost time for the next scheduled dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once. 

Are there any potential side effects from thiamine?

Thiamine may cause the following side effects:

• Pain at injection site (if given by injection into the muscle)

Serious adverse reactions associated with this supplement may occur without warning and could, in rare cases, lead to death. Anaphylactic reactions may occur after rapid or large IV injections. If any of the following signs develop, stop giving thiamine and contact your veterinarian immediately:

• Swelling
• Hives
• Agitation
• Changes in respiration or heart rate
• Collapse
• Severe weakness
• Seizures

Sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting drug/supplement should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this drug/supplement?

DO NOT USE thiamine in:

• Pets who are allergic to it or to any of the ingredients in the supplement.

USE WITH EXTREME CAUTION in:

• Pregnant or nursing animals

Contact your veterinarian if your animal's condition does not improve or worsens despite this treatment. 

Are there any drug interactions I should be aware of?

Certain medications should be used WITH CAUTION when given with thiamine, including:

• Amprolium
• Fluorouracil

Avoid raw fish, shellfish, bacteria, yeast, and fungi while taking this medication. These items contain high concentrations of enzymes called thiaminases, which degrade thiamine. Cooking destroys thiaminases.

Be sure to tell your veterinarian about any medications (including vitamins, supplements or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this supplement?

• Baseline blood work is often required to assess your pet's general health before starting on this supplement. 
• If using the supplement long term, periodic blood work is advised to monitor this supplement's effects on the body. Your veterinarian may adjust the dose based on these results and based on clinical assessment.
• At home, monitor for any abnormal changes. If any occur, discontinue the supplement and contact your veterinarian. 
• Your veterinarian will let you know when they want to reassess your pet to ensure the supplement is working and not causing side effects. 

How do I store thiamine?

• Thiamine HCl for injection should be protected from light and stored at temperatures less than 40°C (104°F) and preferably between 15°C and 30°C (59°F-86°F); avoid freezing.
• Ensure oral supplements are stored in a cool dry area in tightly sealed containers to prevent accidental ingestion.
• Keep out of reach of children.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the supplement/treatment, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms. Report any adverse effects to the FDA or Health Canada.