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Tolfenamic Acid for Veterinary Use
by Barbara Forney, VMD
Tolfenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) and cyclo-oxygenase inhibitor. It is used for the management of both acute and chronic pain in dogs and acute pain for cats. The pharmacologic effects of tolfenamic acid are similar to those of aspirin. It inhibits prostaglandin release and has a direct inhibitory effect on prostaglandin receptors. It also decreases platelet aggregatoin. Tolfenamic acid is well absorbed after oral adminstration. It is generally used as a once a day drug with peak levels occurring at 2-4 hours after administration.
There is active research in humans and dogs regarding the use of tolfenamic acid as an anti-cancer drug. Wilson et al. (J Vet Intern Med 2012) reported on the use of tolfenamic acid in vitro
on canine osteosarcoma, mammary carcinoma, and melanoma cell lines. Tolfenamic acid is an approved veterinary drug in Canada and Eurpote but it is not approved in the United States.
Dog and Cats
Tolfenamic acid may be used by injection intramuscular or subcutaneous or orally. Protocols for using tolfenamic acid in both dogs and cats recommend only administering the drug for 2-5 days followed by a similar number of day without medication. This cycle may be repeated.
- There are relatively few side effects associated with tolfenamic acid. The most common side effects after oral adminstration are vomiting and diarrhea.
- Like other NSAIDs, tolfenamic acid should not be used in animals with active GI bleeding, ulceration or those prone to GI ulcers.
- NSAIDs should be avoided or very carefully monitored in animals with liver or kidney disease.
- Tolfenamic acid should be avoided in animals with known hypersensitivity to other drugs in its class.
- Tolfenamic acid is generally not use presurgically due to decreased platelet aggregation.
- Avoid combining with other anti-inflammatory drugs that tend to predispose animals towards GI ulcers, such as corticosteroids and other NSAIDs.
- Use with caution with drugs that have the potential for renal toxicity, including diuretics, aminoglycoside antibiotics, and amphotericin B.
- Tolfenamic acid should be used with caution with oral anticoagulants, such as warfarin and other coumarin derivatives.
- Tolfenamic acids and other NSAIDs may increase serum digoxin levels. It should not be used in animals receiving methotrexate.
- If an oral overdose is recognized promptly, gut emptying protocols should be instituted.
- Supportive care may include monitoring for GI ulceration, renal function, and electrolyte and fluid status. Dehydrated or debilitated animals are at increased risk for renal failure.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
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