Meclofenamic Acid

Nonsteroidal Anti-inflammatory Drug (NSAID) Fenamate derivative

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 1-2 mg/kg q24h Duration: 3-5 days (max 7 days)
Notes: Administer with food to reduce GI upset. Use lowest effective dose.
Cat PO 0.5-1 mg/kg q24h Duration: 2-3 days (short-term only)
Notes: Use with caution; cats are sensitive to NSAIDs. Monitor for renal and GI effects.
Horse PO 2.2 mg/kg q24h Duration: 5-7 days
Notes: Administer with feed. Not for use in mares intended for breeding.
Cattle PO 2-4 mg/kg q24h Duration: 3-5 days
Notes: For respiratory disease, use as adjunct to antibiotics. Observe withdrawal times.
Small Ruminants PO 2 mg/kg q24h Duration: 3 days
Notes: Extra-label use; limited data. Use with caution.

Clinical Indications & Species Uses

General Indications
  • Anti-inflammatory, analgesic, and antipyretic for musculoskeletal disorders
Dog (Canine)
  • Treatment of musculoskeletal inflammation and pain (e.g., arthritis, soft tissue trauma)
Horse (Equine)
  • Treatment of musculoskeletal inflammation and pain (e.g., laminitis, myositis, arthritis)
Cattle (Bovine)
  • Treatment of respiratory disease (as an adjunct to antimicrobial therapy) and musculoskeletal inflammation

Pharmacology & Mechanism of Action

Drug Class: Nonsteroidal Anti-inflammatory Drug (NSAID) | Pharmacological Group: Fenamate derivative

Mechanism of Action: Meclofenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It exerts its therapeutic effects primarily by inhibiting the cyclooxygenase (COX) enzymes, COX-1 and COX-2, thereby reducing the synthesis of prostaglandins, prostacyclin, and thromboxanes from arachidonic acid. This results in decreased inflammation, pain, and fever. Additionally, meclofenamic acid may modulate the activity of neutrophils and other inflammatory cells, and it has been shown to inhibit the migration of leukocytes to sites of inflammation. Unlike some other NSAIDs, it may also have a direct effect on the inflammatory response by inhibiting the release of lysosomal enzymes and reducing the production of reactive oxygen species.

Pharmacodynamics: Meclofenamic acid produces dose-dependent anti-inflammatory, analgesic, and antipyretic effects. In veterinary species, it is used primarily for its anti-inflammatory properties in musculoskeletal disorders. The drug's potency is comparable to other NSAIDs such as phenylbutazone and flunixin meglumine. Its onset of action is relatively rapid, with peak effects occurring within a few hours after oral administration. The duration of action is typically 12-24 hours, depending on the species and dosage. Meclofenamic acid also has a mild anti-endotoxic effect, which may be beneficial in certain conditions. It does not have significant immunosuppressive effects at therapeutic doses.

⚑ Pharmacokinetics Summary

Absorption: Meclofenamic acid is well absorbed after oral administration in most species. In horses, peak plasma concentrations are reached within 1-2 hours. In cattle, absorption is slower, with peak levels occurring at approximately 4-6 hours. Food may delay absorption but does not significantly reduce the extent of absorption. In dogs and cats, oral bioavailability is high, around 80-90%.
Distribution: Meclofenamic acid is highly bound to plasma proteins (greater than 99%), primarily to albumin. It distributes widely into tissues, with high concentrations found in synovial fluid, which is beneficial for treating joint inflammation. It crosses the placenta and is excreted in milk, although concentrations are low. The volume of distribution is relatively small, consistent with its high protein binding.
Metabolism: Meclofenamic acid undergoes extensive hepatic metabolism, primarily via oxidation and glucuronide conjugation. The major metabolites are hydroxylated derivatives and their glucuronides. Some metabolites retain pharmacological activity, contributing to the overall effect. Enterohepatic recirculation occurs, which may prolong the drug's presence in the body.
Excretion: Excretion is primarily via the kidneys, with about 70-80% of the dose eliminated in urine as metabolites and conjugates. A smaller portion is excreted in feces via bile. The elimination half-life varies by species: approximately 2-3 hours in dogs, 4-6 hours in cats, 1-2 hours in horses, and 2-4 hours in cattle. However, the duration of action may be longer due to tissue distribution and enterohepatic recirculation.
Half-Life: Dog: 2-3 hours; Cat: 4-6 hours; Horse: 1-2 hours; Cattle: 2-4 hours
Bioavailability: Oral: ~80-90% in dogs and cats; ~70% in horses; ~60% in cattle
Protein Binding: >99% (primarily albumin)

Available Formulations & Strengths

Oral Tablet 50 mg, 100 mg (PO)
Oral Granules 10% w/w (PO)
Injectable Solution 10% (100 mg/mL) (IV, IM)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to meclofenamic acid or other NSAIDs
  • Active gastrointestinal ulceration or bleeding
  • Renal or hepatic impairment
  • Dehydration or hypovolemia
  • Concurrent use of other NSAIDs or corticosteroids
  • Pregnancy (especially in horses and cattle) unless benefit outweighs risk
  • In animals with bleeding disorders
Warnings & Clinical Precautions:
  • Use with caution in geriatric animals or those with pre-existing renal, hepatic, or cardiac disease.
  • Monitor for signs of gastrointestinal toxicity (vomiting, diarrhea, melena).
  • Ensure adequate hydration before and during therapy.
  • Avoid use in animals with suspected or confirmed GI ulcers.
  • In food animals, observe withdrawal times.
  • Not recommended for use in cats due to increased sensitivity to NSAIDs.
  • Use lowest effective dose for shortest duration.
  • Do not use in animals with known hypersensitivity to other fenamates (e.g., flunixin).

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (vomiting, diarrhea, anorexia)
  • Elevated liver enzymes
  • Renal effects (increased BUN/creatinine)

Serious / Severe:

  • Gastrointestinal ulceration and perforation
  • Acute renal failure
  • Hepatotoxicity
  • Bone marrow suppression (rare)
  • Anaphylaxis (rare)

Rare:

  • Blood dyscrasias (thrombocytopenia, leukopenia)
  • Neurological signs (ataxia, seizures)
  • Dermatological reactions (rash, pruritus)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Other NSAIDs (e.g., flunixin, phenylbutazone) Increased risk of gastrointestinal ulceration and renal toxicity High
Corticosteroids Increased risk of GI ulceration and perforation High
Anticoagulants (e.g., warfarin) Increased risk of bleeding due to platelet inhibition and protein binding displacement High
Aminoglycosides Increased risk of nephrotoxicity Moderate
Diuretics (e.g., furosemide) Reduced diuretic efficacy and increased risk of renal toxicity Moderate
ACE inhibitors Reduced antihypertensive effect and increased risk of renal impairment Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea (possibly bloody)
  • Depression
  • Ataxia
  • Seizures
  • Renal failure
  • Hepatic failure
  • Coma

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce emesis if ingestion is recent (within 2 hours) and the animal is conscious. Administer activated charcoal to reduce absorption. Provide intravenous fluids to maintain renal perfusion and correct dehydration. Monitor renal and hepatic function. Use gastroprotective agents (e.g., misoprostol, omeprazole) to prevent GI ulceration. In severe cases, consider hemodialysis or peritoneal dialysis to enhance elimination.

Food Animal Withdrawal Times

πŸ₯© Meat: 7 daysπŸ₯› Milk: 3 days

Withdrawal times are based on label recommendations for cattle. For other species, consult regulatory guidelines. Extra-label use may require extended withdrawal periods.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25Β°C (68-77Β°F)

Handling & Special Conditions: Protect from moisture. Keep container tightly closed.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in horses and cattle in the US (e.g., Arquel). Not approved for dogs and cats, but may be used extra-label.

Extra-Label (Off-Label) Use: In the US, extra-label use of meclofenamic acid in food animals is permitted under AMDUCA, but requires a valid veterinary-client-patient relationship and extended withdrawal times. Not approved for use in cats or small ruminants.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Meclofenamic acid is a potent NSAID used primarily in horses and cattle for musculoskeletal inflammation. It is not a first-line choice in small animals due to the availability of safer NSAIDs. In horses, it is particularly effective for laminitis and myositis. In cattle, it is used as an adjunct to antimicrobial therapy for respiratory disease. The drug has a narrow therapeutic index, and overdose can be fatal. Always use the lowest effective dose for the shortest duration. Monitor for adverse effects, especially gastrointestinal and renal. In food animals, adhere to withdrawal times. Due to its high protein binding, drug interactions are common. Avoid concurrent use with other NSAIDs or corticosteroids. In cats, use is discouraged due to increased sensitivity and risk of toxicity. For pain management in dogs and cats, consider alternative NSAIDs with better safety profiles (e.g., carprofen, meloxicam).

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)