Piroxicam

Nonsteroidal Anti-inflammatory Drug (NSAID) Oxicam derivative

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 0.3 mg/kg q48h (every 48 hours) Duration: Variable; for osteoarthritis, often long-term; for TCC, often used with chemotherapy
Notes: Administer with food to reduce GI upset. Use lowest effective dose.
Cat PO 0.3 mg/kg q48h (every 48 hours) Duration: Short-term only; not recommended for chronic use
Notes: Extreme caution; monitor for renal and GI toxicity. Not FDA-approved for cats.
Horse PO 0.4 mg/kg q24h (every 24 hours) Duration: 3-5 days
Notes: Not commonly used; phenylbutazone or flunixin meglumine preferred.
Cattle PO 0.5 mg/kg q24h Duration: 3-5 days
Notes: Not approved; extra-label use only with veterinary supervision.

Clinical Indications & Species Uses

General Indications
  • Pain and inflammation management in dogs
Dog (Canine)
  • Osteoarthritis
  • Musculoskeletal pain
  • Post-operative pain
  • Canine transitional cell carcinoma (adjunctive therapy)
Horse (Equine)
  • Musculoskeletal pain
  • Inflammation
  • Colic (not first-line)

Pharmacology & Mechanism of Action

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

Mechanism of Action: Piroxicam is a nonselective inhibitor of cyclooxygenase (COX-1 and COX-2) enzymes, thereby blocking the conversion of arachidonic acid to prostaglandins and thromboxanes. This reduces inflammation, pain, and fever. It also inhibits neutrophil migration and lysosomal enzyme release, contributing to its anti-inflammatory effects.

Pharmacodynamics: Piroxicam has potent anti-inflammatory, analgesic, and antipyretic properties. It is more selective for COX-1 than COX-2, which may explain its higher incidence of gastrointestinal ulceration compared to some other NSAIDs. It also has anti-tumor effects in some animal models, possibly through inhibition of angiogenesis and induction of apoptosis.

⚑ Pharmacokinetics Summary

Absorption: Well absorbed after oral administration in most species. In dogs, peak plasma concentrations occur within 3-5 hours. Food may delay absorption but not the extent.
Distribution: Widely distributed in tissues. High protein binding (approximately 90-99% in dogs and humans). Penetrates into synovial fluid and other inflamed tissues.
Metabolism: Extensively metabolized in the liver via hydroxylation and conjugation. The major metabolite is 5'-hydroxypiroxicam, which is pharmacologically inactive.
Excretion: Excreted primarily in the urine (about 60%) and feces (about 40%) as metabolites. In dogs, biliary excretion and enterohepatic recirculation occur, contributing to a long half-life.
Half-Life: Dog: approximately 40 hours; Cat: approximately 10-15 hours; Horse: approximately 4-6 hours; Cattle: approximately 20-30 hours.
Bioavailability: Oral bioavailability is high, approximately 80-100% in dogs and cats.
Protein Binding: Approximately 90-99% in dogs and humans; lower in cats (around 80%).

Available Formulations & Strengths

Oral Capsule 10 mg, 20 mg (PO)
Oral Tablet 10 mg, 20 mg (PO)
Injectable Solution (not commonly used in veterinary medicine) 20 mg/mL (IM/IV)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to piroxicam or other NSAIDs
  • Active gastrointestinal ulceration or bleeding
  • Renal or hepatic impairment
  • Dehydration or hypovolemia
  • Concurrent use of corticosteroids or other NSAIDs
  • Pregnancy or lactation (unless benefits outweigh risks)
  • In cats, use is contraindicated due to high risk of toxicity
Warnings & Clinical Precautions:
  • Use with caution in geriatric or debilitated animals
  • Monitor renal function, liver enzymes, and blood counts during long-term therapy
  • Administer with food to reduce GI irritation
  • Avoid in animals with bleeding disorders
  • Use lowest effective dose for shortest duration
  • In food animals, observe withdrawal times; not approved for use in food animals in many countries

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (vomiting, diarrhea, anorexia)
  • Elevated liver enzymes
  • Renal toxicity (especially in dehydrated animals)

Serious / Severe:

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

Rare:

  • Skin reactions
  • Blood dyscrasias
  • Neurological signs (seizures, ataxia)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Corticosteroids Increased risk of gastrointestinal ulceration and renal toxicity High
Other NSAIDs (e.g., aspirin, carprofen) Additive toxicity, especially GI and renal High
Anticoagulants (e.g., warfarin) Increased risk of bleeding due to platelet inhibition High
ACE inhibitors (e.g., enalapril) Reduced renal blood flow, increased risk of renal failure Moderate
Diuretics (e.g., furosemide) Reduced efficacy of diuretics and increased risk of renal toxicity Moderate
Methotrexate Increased methotrexate toxicity due to reduced renal clearance Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea (possibly bloody)
  • Lethargy
  • Loss of appetite
  • Abdominal pain
  • Renal failure (oliguria/anuria)
  • Seizures
  • Coma

Emergency Treatment Protocol: Induce vomiting if within 2 hours of ingestion (in conscious animals). Administer activated charcoal to reduce absorption. Provide supportive care: IV fluids to maintain renal perfusion, gastroprotective agents (e.g., sucralfate, omeprazole), and monitor renal and hepatic function. In severe cases, consider hemodialysis or peritoneal dialysis.

Food Animal Withdrawal Times

πŸ₯© Meat: 30 daysπŸ₯› Milk: 7 days

Piroxicam is not approved for use in food animals in the US; withdrawal times are extrapolated from other NSAIDs and may not be reliable. Consult regulatory authorities for specific guidance.

Storage, Handling & Regulatory Information

Storage Temperature: Store at 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: Not FDA-approved for veterinary use; used extra-label in dogs and cats. Human-approved formulations are available.

Extra-Label (Off-Label) Use: In the US, extra-label use of piroxicam in food animals is prohibited by the FDA due to lack of established withdrawal times and potential for violative residues. In dogs and cats, extra-label use is permitted under AMDUCA with appropriate veterinary oversight.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Piroxicam is a long-acting NSAID primarily used in dogs for osteoarthritis and as an adjunctive treatment for transitional cell carcinoma (TCC) of the bladder. Its long half-life allows every-other-day dosing, which may improve owner compliance. However, its nonselective COX inhibition increases the risk of gastrointestinal and renal adverse effects compared to newer COX-2 selective NSAIDs. It is not recommended for cats due to a narrow therapeutic index and high risk of toxicity. In horses, other NSAIDs are preferred. Always use the lowest effective dose for the shortest duration, and monitor for adverse effects, especially in geriatric or debilitated patients. For TCC, piroxicam is often used in combination with mitoxantrone or other chemotherapeutic agents, and its anti-tumor effects are thought to be independent of COX inhibition.

References & Literature

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