What is white willow bark?
White willow bark is a supplement made from the bark of the white willow tree (Salix alba). The active ingredient in white willow bark is salicin, which is similar to the active ingredient in aspirin. It is most often used to treat pain and inflammation associated with arthritis and to treat fever. It has also been used to prevent blood clots associated with heart disease, although its effectiveness for this purpose is in question. It is used in both dogs and cats.
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 is white willow bark given?
White willow bark comes in capsule, liquid, and powder forms.
- All forms are given orally (by mouth).
- Give this supplement with food, as dosing on an empty stomach may cause stomach upset.
- Measure liquid forms carefully, especially in cats, as they are more susceptible to toxicity.
- Follow your veterinarian’s instructions on administering this medication carefully and give for the entire time prescribed by your veterinarian, even if your pet is feeling better.
What if I miss giving my pet the supplement?
If you miss a dose, give it as soon as you remember and then wait the recommended time for the next dose, as prescribed by your veterinarian. Do not give the pet two doses at once.
Are there any potential side effects?
White willow bark may cause the following side effects:
- Vomiting
- Loss of appetite
Serious adverse reactions may occur. If any of the following signs develop, stop giving white willow bark 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. It can take up to several weeks for full effects of the supplement to be seen, and it should stop working within a few days, although effects may last longer in pets with liver and/or kidney disease.
Are there any risk factors for this supplement?
DO NOT USE in:
- Pets that are allergic to aspirin or similar medications
- Pets that are pregnant or nursing
USE WITH CAUTION in:
- Pets with asthma or other breathing problems
- Pets with stomach ulcers or other gastrointestinal problems
- Pets with bleeding disorders
- Pets that are young
Are there any drug interactions I should be aware of?
The following medications should be used with caution when given with white willow bark:
- Nonsteroidal anti-inflammatory drugs (NSAIDs), such as meloxicam and robenacoxib
- Beta-blockers (e.g., atenolol, propranolol)
- Diuretics (e.g., furosemide, spironolactone)
- Methotrexate
- Phenytoin
- Warfarin and other blood thinners
Be sure to tell your veterinarian about any medications (including 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 side effects such as those noted above. If any side effects occur, discontinue the supplement, and contact your veterinarian.
How do I store white willow bark?
- Store the supplement according to the manufacturer’s directions.
- Protect from light, moisture, and heat.
- 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 supplement, 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.
