Piroxicam
Piroxicam is a non-steroidal anti-inflammatory drug (NSAID) of the oxicam class. While it possesses standard NSAID properties (anti-inflammatory, analgesic, and antipyretic), its primary use in veterinary medicine is as an **adjunctive treatment for transitional cell carcinoma (TCC)** of the bladder in dogs, as well as other neoplasms like squamous cell carcinomas and mammary adenocarcinomas. > **Clinical Pearl:** Piroxicam has a very narrow therapeutic index in dogs and cats compared to newer, COX-2 selective NSAIDs. It is rarely used solely for osteoarthritis pain today due to the high risk of gastrointestinal ulceration. It is increasingly used in **metronomic (low-dose, continuous) chemotherapy** protocols alongside drugs like cyclophosphamide to prevent sarcoma recurrence by inhibiting angiogenesis and modulating the immune system.
Mechanism: Like other NSAIDs, piroxicam non-selectively inhibits **cyclooxygenase (COX)** enzymes, thereby blocking the conversion of arachidonic acid to **prostaglandins** and thromboxanes. This reduces inflammation and pain. Its **anti-tumor effects** are not fully understood but are believed to be indirect. Mechanisms include: * **Inhibition of COX-2** expressed by tumor cells (especially TCC) * **Anti-angiogenesis** (preventing new blood vessel formation to the tumor) * **Immune system modulation** * Inhibition of superoxide formation
Dosing by species
- Adjunctive therapy of transitional cell carcinomas ยท 0.3 mg/kg PO q24-72h ยท PO ยท q24-72h ยท Gastric protectants may be useful. Use with caution in pre-existing renal disease.
- Adjunctive therapy of transitional cell carcinomas/neoplastic diseases ยท 0.3 mg/kg PO every 24-48 hours ยท PO ยท q24-48h
- Cancer pain ยท 0.3 mg/kg PO q24-48h or 1 mg (total dose) per cat PO q24h ยท PO ยท q24-48h ยท Maximum of 7 days
- Antiinflammatory/analgesic ยท 1 mg per cat (total dose) PO once daily ยท PO ยท q24h ยท Maximum of 7 days
- Idiopathic chronic rhinosinusitis ยท 0.3 mg/kg PO once daily or every other day ยท PO ยท q24-48h
- All uses (e.g., various neoplasms) ยท 0.3 mg/kg ยท PO ยท q24-96h ยท Long-term ยท Start at least frequent administration and slowly increase if no side effects observed.
- Mucocutaneous squamous cell carcinoma ยท 80 mg (total dose) PO once daily ยท PO ยท q24h ยท Dose was eventually reduced to every other day or every third day due to colic signs.
- Squamous cell carcinoma of the third eyelid after surgical excision ยท 80 mg (total dose) PO once daily ยท PO ยท q24h
- Fracture associated limb swelling (Rabbits) ยท 0.1-0.2 mg/kg PO q8h ยท PO ยท q8h ยท 3 weeks
Routes of administration
Contraindications
- Hypersensitivity to piroxicam, aspirin, or other NSAIDs
- Active or history of gastrointestinal ulcer disease
- Bleeding disorders
- Gastric ulceration
- Renal disease
- Concurrent use of corticosteroids
- Concurrent use of other NSAIDs
- Dehydration (relative contraindication due to renal risk)
Adverse effects
- Gastrointestinal ulceration and bleeding (melena, hematemesis)
- Vomiting, anorexia, and diarrhea
- Renal papillary necrosis
- Peritonitis (secondary to GI perforation)
- Decreased hematocrit (anecdotal in cats)
- Peripheral edema
- Elevated liver enzymes
- Gastrointestinal toxicity
- Gastric ulceration
- Ulcerative skin lesions (reported in cats)
- Potential precipitation of cardiac failure (known in humans, unknown risk in animals)
Drug interactions
- Aminoglycosides (gentamicin, amikacin) ยท Increased risk for nephrotoxicity
- Anticoagulants (heparin, LMWH, warfarin) ยท Increased risk for bleeding
- Aspirin ยท Decreased piroxicam plasma levels and increased likelihood of GI adverse effects (blood loss); do not use concurrently
- Bisphosphonates (alendronate) ยท May increase risk for GI ulceration
- Cisplatin ยท May potentiate the renal toxicity of cisplatin
- Corticosteroids ยท Significantly increased risk for GI adverse effects and ulceration ยท major
- Furosemide ยท May reduce the saluretic and diuretic effects of furosemide
- Highly protein-bound drugs (phenytoin, valproic acid, sulfonamides) ยท Piroxicam is 99% protein-bound and may displace other drugs, increasing their serum levels and duration of action
- Methotrexate ยท Serious toxicity has occurred when used concomitantly; use with extreme caution
- Other NSAIDs ยท Increased risk of severe gastric ulceration and GI toxicity ยท major
- Diuretics ยท Increased risk of nephrotoxicity and renal papillary necrosis ยท moderate
- Aminoglycosides ยท Increased risk of nephrotoxicity ยท moderate
Monitoring
- Adverse Effects (particularly GI bleeding: melena, hematemesis, pale mucous membranes)
- Liver function tests (occasionally with chronic use)
- Renal function tests (occasionally with chronic use)
- Renal function (BUN, Creatinine, SDMA, Urinalysis)
- Liver enzymes
- Clinical signs of GI ulceration (vomiting, melena, anorexia)
- Hydration status
- Skin integrity (especially in cats)
Overdose
Overdosage can lead to severe **gastrointestinal (ulceration, perforation)** and **renal (papillary necrosis, failure)** effects. Dogs may be more sensitive to the ulcerative effects than humans. **Treatment:** * Decontamination with emetics and/or activated charcoal if recent. * Gastrointestinal protectants (e.g., misoprostol, omeprazole, sucralfate) are strongly warranted. * Fluid diuresis should be considered to protect renal function. * Monitor carefully and provide supportive care.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.