Antioxidants

What are antioxidants?

Antioxidants are dietary supplements that protect against cellular damage caused by reactive compounds, such as free radicals or hydrogen peroxide. These reactive compounds are produced as a by-product of inflammation.

When inflammation is chronic, the body’s natural antioxidants may become depleted and supplementation may be needed. When reactive compounds accumulate in the cells, DNA damage, and eventually cancer, can develop. Antioxidants are used in cats, dogs, birds, guinea pigs, rabbits, and other animals.

Antioxidants may include vitamins, minerals, amino acids, herbs, botanicals, enzymes, or other nutraceuticals. Some examples include vitamin C, vitamin E, selenium, and glutathione peroxidase. 

While many supplements are sold over the counter, they contain ingredients that have biological effects that should be managed by your veterinarian. Follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

The U.S. Food and Drug Administration (FDA) does not review non-drug health products (e.g., herbals, nutraceuticals, shampoos, and other supplements) for safety or effectiveness before they are sold to the public. Manufacturers of non-drug health products must ensure their products are safe and labeled accurately. 

The FDA requires that these non-pharmaceuticals contain a disclaimer that says, “This product is not intended to diagnose, treat, cure or prevent any disease.” Health Canada licenses “veterinary health products” after reviewing safety, efficacy, and manufacturing information provided by the manufacturer. These products are not tested by Health Canada.

Your veterinarian is the best source of information about the safety of non-drug health products in pets. Just because a product 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 also may be incomplete and may not represent the full range of effects the supplement could have on your pet.

How are antioxidants given?

• Antioxidants come in liquid, tablet, capsule, and other forms. Injectable forms may be administered by your veterinarian in hospital.
• Antioxidants administered at home are given orally (by mouth).
• Oral forms may be given with or without food.
• Measure liquid doses carefully.
• Dose vitamin A and other fatty vitamins very carefully, as high doses are toxic.
• Follow your veterinarian’s instructions on administering this medication and give for the entire time prescribed by your veterinarian, even if your pet is feeling better.

This medication should take effect within a few hours to a few days, though outward effects may not be noticeable.

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?

Antioxidants may cause the following side effects:

• Mild gastrointestinal upset

Serious adverse reactions may occur. If any of the following signs develop, stop giving antioxidants and contact your veterinarian immediately:

• An allergic reaction, such as irregular breathing, rash, fever, puffiness and swelling around the face

Drug 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 medication should stop working within 1–2 days, although effects may last longer in pets with liver and/or kidney disease, and depending on the type of antioxidant given.

Are there any risk factors for this supplement?

DO NOT USE antioxidants in:

• Pets that are allergic to any component of the medication

USE WITH CAUTION in:

• Pets that are pregnant

Are there any drug interactions I should be aware of?

There are no known general antioxidant drug interactions. However, always follow your veterinarian’s instructions and read the supplement label for any known drug interactions.

Vitamins, herbal therapies, and supplements have the potential to interact with each other, as well as with prescription and over-the-counter medications. Be sure to tell your veterinarian about any medications (including all vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this supplement?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the supplement is working and not causing side effects.
• At home, monitor for any abnormal changes. If any occur, discontinue the medication and contact your veterinarian.

How do I store antioxidants?

• Store the medication in a cool, dry location.
• Follow the manufacturer’s recommended storage directions.
• Keep the container out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, 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.