Tolfenamic Acid
N-(2-methyl-3-chlorophenyl)anthranilic acid
Also known as: Tolfedine · Tolfejec · acidum tolfenamicum · Bifenac · Clotam · Clotan · Flocur · Gantil · Migea · Polmonin · Purfalox · Rociclyn · Tolfamic · Turbaund
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceNSAID (extra-label) — Acute pain
Verified clinician required
- q24h
NA
Governing clinical context (3)
- NSAID (extra-label):
- Unless otherwise labeled, store tolfenamic acid products at room temperature. Protect from light. Refer to the injectable product label for discard dating following the first vial puncture.
- ■ Should give oral medicine with food.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Tolfenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid (fenamate) class, chemically related to meclofenamic acid. It is utilized primarily for its analgesic, anti-inflammatory, and antipyretic properties.
Key Clinical Features:
- Dual Action: Unlike many traditional NSAIDs, fenamates like tolfenamic acid not only inhibit prostaglandin synthesis but also directly block prostaglandin receptors, potentially offering enhanced analgesic efficacy.
- Pulse Dosing: For chronic conditions in dogs, it is uniquely prescribed on a "pulse" schedule (e.g., 3-5 consecutive days per week) to minimize gastrointestinal and renal toxicity while maintaining efficacy.
- Platelet Effects: It possesses significant anti-thromboxane activity, which impairs platelet aggregation. Therefore, it is not recommended for pre-surgical use.
- Availability: While widely approved in Canada, Europe, and Australia for small and large animals, it is currently not available in the USA.
Clinical Pearl: Because enterohepatic recirculation is increased when given with food, administering tolfenamic acid with a meal can increase its bioavailability, though it may also increase absorption variability compared to a fasted state.
Mechanism of action
Tolfenamic acid exerts its effects through multiple pathways in the inflammatory cascade:
- Cyclooxygenase (COX) Inhibition: It is a potent inhibitor of the COX enzyme, which prevents the conversion of arachidonic acid → prostaglandins (PGs) and thromboxanes (TXA2). This reduces inflammation, pain, and fever.
- Direct Receptor Antagonism: Uniquely among NSAID classes, fenamates directly block the binding of synthesized prostaglandins to their respective tissue receptors (e.g., EP receptors), providing a secondary mechanism of action against pain and inflammation.
- Anti-thromboxane Activity: By inhibiting TXA2 synthesis, it significantly impairs platelet aggregation and normal clotting function.
Safety & warnings
Contraindications
- Hypersensitivity to tolfenamic acid or other fenamates (e.g., meclofenamic acid)
- Active gastrointestinal bleeding or ulceration
- Pre-surgical administration (due to anti-thromboxane/platelet effects)
- Dehydrated, hypovolemic, or hypotensive patients
- Patients with gastrointestinal disease
- Patients with blood clotting problems
- Pregnant animals
- Animals under 6 weeks of age
- Intramuscular (IM) administration in cats
Adverse effects
- Gastrointestinal ulceration (at high doses)
- Platelet dysfunction/prolonged bleeding time
- Potential nephrotoxicity (especially in dehydrated patients)
- Gastrointestinal signs (vomiting, diarrhea, anorexia)
- Gastrointestinal ulceration and bleeding
- Renal toxicity (especially during hypotension)
- Potential precipitation of cardiac failure (rare/unknown risk in animals)
Precautions
Use with extreme caution in patients with decreased renal or hepatic function. Ensure patients are well-hydrated to mitigate nephrotoxic risks. Like other NSAIDs, tolfenamic acid should be used with caution during pregnancy. Do not use pre-surgically due to its effects on platelet function.
Drug interactions
May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea).
Concomitant therapy may increase the occurrence of gastric ulceration; avoid concurrent use.
NSAIDs may increase serum levels of digoxin.
May increase plasma levels of NSAIDs; potentially affects tolfenamic acid levels in dogs.
NSAIDs may reduce the saluretic and diuretic effects of furosemide.
Serious toxicity has occurred with concomitant NSAID use; use together with extreme caution.
May enhance the risk of nephrotoxicity.
May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea).
Tolfenamic acid is 98-99% protein-bound; may displace highly protein-bound drugs like warfarin, increasing bleeding risk. Monitor closely.
Increased risk of gastrointestinal ulceration and bleeding. Do not administer concurrently or within 24 hours.
Increased risk of nephrotoxicity.
Monitoring
- Clinical efficacy (pain scores, resolution of inflammation)
- Adverse effects (vomiting, diarrhea, anorexia)
- Renal function (BUN, Creatinine, SDMA, USG) with prolonged use
- Signs of GI bleeding (melena, pale mucous membranes)
- Clinical signs of gastrointestinal toxicity (vomiting, diarrhea, melena, anorexia)
- Renal parameters (BUN, creatinine, USG), especially in perioperative or hypotensive patients
- Liver enzymes in patients receiving prolonged therapy
Pharmacokinetics
Half-life
Absorption
Absorbed after oral administration. Peak levels in dogs occur 2-4 hours post-dosing. Enterohepatic recirculation is increased with food, which increases bioavailability but also creates more variability compared to fasted dogs.
Distribution
Volume of distribution in dogs is approximately 1.2 L/kg. Highly protein bound (98-99%).
Metabolism
Undergoes hepatic metabolism and enterohepatic recycling.
Elimination
Clearance is significantly increased in dogs with experimentally induced renal failure, presumably via increased hepatic metabolism or enterohepatic recycling. Duration of anti-inflammatory effect is 24-36 hours.
Overdose
Acute toxicity data is limited. Experimental studies in dogs and cats did not demonstrate significant renal or GI toxicity until doses exceeded 10 times the labeled dose.
Treatment Protocol:
- Decontamination: Empty the gut following recent oral ingestion (emesis induction, activated charcoal).
- Supportive Care: Institute IV fluid therapy to maintain hydration and support renal perfusion.
- Seizure Control: Use IV diazepam if seizures occur.
- Monitoring: Closely monitor for signs of gastrointestinal bleeding (melena, hematemesis). Monitor electrolyte and fluid balance carefully, and manage any acute renal failure using established veterinary guidelines.
Available products
Formulations
- Tablets
- Injection (Solution)
- 40 mg/ml injectable solution
- 6 mg oral tablet
- 20 mg oral tablet
- 60 mg oral tablet
Veterinary
- Tolfenamic Acid Tablets: 6 mg, 30 mg, 60 mg
- Tolfenamic Acid Injection: 40 mg/mL
- Tolfedine 40 mg/ml solution for injection
- Tolfedine 6 mg tablets
- Tolfedine 20 mg tablets
- Tolfedine 60 mg tablets
Human-labeled
- None in the USA
Regulatory status
Authorized for preoperative administration to cats and dogs.
POM-V classification.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Unless otherwise labeled, store tolfenamic acid tablets and solution at room temperature.
Client information
Tolfenamic acid is a medication used to relieve pain and inflammation in your pet.
Important Administration Guidelines:
- Follow the Schedule: If your veterinarian prescribed a weekly dosing regimen (e.g., giving the medication for 3 to 5 consecutive days, then stopping for the rest of the week), it is critical to follow this exactly. This "pulse" schedule helps prevent serious side effects.
- Give with Food: Administering this medication with a meal can help your pet absorb it better and may reduce stomach upset.
- What to Watch For: Stop the medication and contact your veterinarian immediately if your pet experiences vomiting, diarrhea, loss of appetite, increased thirst/urination, or if you notice dark, tarry stools (which can be a sign of stomach bleeding).
- Do Not Mix Medications: Never give your pet human pain relievers (like aspirin or ibuprofen) or other veterinary NSAIDs while they are taking tolfenamic acid, as this can cause fatal stomach ulcers or kidney failure.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.