Tolfenamic Acid

Also used with Antibiotics as associative treatment

it should not be used in animals with active GI bleeding or ulceration. Use with caution in patients with decreased renal or hepatic function.

Tolfenamic acid exhibits pharmacologic actions similar to those of aspirin. It is a potent inhibitor of cyclooxygenase, thereby inhibiting the release of prostaglandins. It also has direct inhibition of prostaglandin receptors. Tolfenamic acid has significant anti thromboxane activity and is not recommended for use pre-surgically because of its effects on platelet function.

Pharmacokinetics: Tolfenamic acid is absorbed after oral administration. In dogs, peak levels occur from 2–4 hours after dosing. Enterohepatic recirculation is increased if given with food. This can increase the bioavailability, but also creates more variability in bioavailability than when given to fasted dogs. The volume of distribution in dogs is reported to be 1.2 L/kg and it has an elimination half-life of about 6.5 hours. Duration of antiinflammatory effect is 24–36 hours. Dogs with experimentally induced renal failure had significantly increased clearances of the drug presumably via increasing hepatic metabolism or enterohepatic recycling of tolfenamic acid

The following drug interactions have either been reported or are theoretical in
humans or animals receiving tolfenamic acid or other NSAIDs and may be of
significance in veterinary patients:

ASPIRIN: May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea)
CORTICOSTEROIDS: As concomitant corticosteroid therapy may increase the occurrence of gastric ulceration, avoid the use of these drugs when also using tolfenamic acid
DIGOXIN: NSAIDS may increase serum levels
FLUCONAZOLE: Administration has increased plasma levels of celecoxib in humans and potentially could also affect tolfenamic acid levels in dogs
FUROSEMIDE: NSAIDs may reduce saluretic and diuretic effects
METHOTREXATE: Serious toxicity has occurred when NSAIDs have been used concomitantly with methotrexate; use together with extreme caution
NEPHROTOXIC DRUGS (e.g., furosemide, aminoglycosides, amphotericin B, etc.): May enhance the risk of nephrotoxicity
NSAIDS, OTHER: May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea)
WARFARIN: Closely monitor patients also receiving drugs that are highly
bound to plasma proteins (e.g., warfarin), as tolfenamic acid and its active
metabolite are 98–99% protein bound in the dog

Tolfenamic acid is relatively safe when given as recommended in dogs and cats. Vomiting and diarrhea have been reported after oral use. Experimental studies did not demonstrate significant renal or GI toxicity until doses were more than 10 times labeled.
Because of its anti-thromboxane activity and resultant effects on platelet function, tolfenamic acid is not recommended for use pre-surgically.

No specific information was located. Monitor for GI bleeding. Because tolfenamic acid may cause renal effects, monitor electrolyte and fluid balance carefully and manage renal failure using established guidelines.

Cattle: Meat withdrawal = 10 days (IM), 4 days (IV); Milk withdrawal = 12 hours (1
milking).

Swine: Meat withdrawal = 6 days.