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.
Mecanismo: 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
Dosificación por especie
- Adjunctive therapy of transitional cell carcinomas · 0.3 mg/kg PO q24-72h · PO · q24-72h · Gastric protectants may be useful. Use with caution in pre-existing renal disease.
- Adjunctive therapy of transitional cell carcinomas/neoplastic diseases · 0.3 mg/kg PO every 24-48 hours · PO · q24-48h
- Cancer pain · 0.3 mg/kg PO q24-48h or 1 mg (total dose) per cat PO q24h · PO · q24-48h · Maximum of 7 days
- Antiinflammatory/analgesic · 1 mg per cat (total dose) PO once daily · PO · q24h · Maximum of 7 days
- Idiopathic chronic rhinosinusitis · 0.3 mg/kg PO once daily or every other day · PO · q24-48h
- All uses (e.g., various neoplasms) · 0.3 mg/kg · PO · q24-96h · Long-term · Start at least frequent administration and slowly increase if no side effects observed.
- Mucocutaneous squamous cell carcinoma · 80 mg (total dose) PO once daily · PO · q24h · 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 · 80 mg (total dose) PO once daily · PO · q24h
- Fracture associated limb swelling (Rabbits) · 0.1-0.2 mg/kg PO q8h · PO · q8h · 3 weeks
Vías de administración
Contraindicaciones
- 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)
Efectos adversos
- 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)
Interacciones farmacológicas
- Aminoglycosides (gentamicin, amikacin) · Increased risk for nephrotoxicity
- Anticoagulants (heparin, LMWH, warfarin) · Increased risk for bleeding
- Aspirin · Decreased piroxicam plasma levels and increased likelihood of GI adverse effects (blood loss); do not use concurrently
- Bisphosphonates (alendronate) · May increase risk for GI ulceration
- Cisplatin · May potentiate the renal toxicity of cisplatin
- Corticosteroids · Significantly increased risk for GI adverse effects and ulceration · major
- Furosemide · May reduce the saluretic and diuretic effects of furosemide
- Highly protein-bound drugs (phenytoin, valproic acid, sulfonamides) · Piroxicam is 99% protein-bound and may displace other drugs, increasing their serum levels and duration of action
- Methotrexate · Serious toxicity has occurred when used concomitantly; use with extreme caution
- Other NSAIDs · Increased risk of severe gastric ulceration and GI toxicity · major
- Diuretics · Increased risk of nephrotoxicity and renal papillary necrosis · moderate
- Aminoglycosides · Increased risk of nephrotoxicity · moderate
Monitoreo
- 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)
Sobredosis
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.
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