Piroxicam

Piroxicam is an oxicam nonsteroidal anti-inflammatory drug with analgesic and anti-inflammatory effects. A distinctive veterinary application is treatment of selected canine tumors, particularly urothelial carcinoma. It may be used alone or within an oncology protocol. Clinical response depends on tumor biology, and its oncologic role extends beyond relief of inflammatory pain.

Group

Oxicam nonsteroidal anti-inflammatory drug

Mechanism of Action

Piroxicam inhibits cyclooxygenase-mediated prostaglandin synthesis, reducing inflammatory signaling and sensitization of nociceptors. In some tumors, altered prostaglandin signaling may affect proliferation, angiogenesis, apoptosis and local immune responses. Additional cyclooxygenase-independent effects have been proposed. The exact combination of mechanisms responsible for antitumor responses in individual veterinary cancers remains incompletely defined.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Musculoskeletal pain	0.3 mg/kg	PO	Every 48 h
Adjunctive cancer treatment — Initial	0.3 mg/kg	PO	Every 24 h	Initial daily stage; then transition to the separately listed 48-hour schedule according to response and tolerance.
Adjunctive cancer treatment — Maintenance	0.3 mg/kg	PO	Every 48 h
Cancer pain	0.3 mg/kg	PO	Every 24–48 h
Lymphoplasmacytic rhinitis adjunct	0.3 mg/kg	PO	Every 24 h	Described with doxycycline 3–5 mg/kg PO q12h or azithromycin 5 mg/kg PO q24h. At 2 weeks, if improved, reduce doxycycline to daily or azithromycin to twice weekly; piroxicam remains daily. Courses may last at least 6 months; reassess benefit and toxicity.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Selected pain or cancer treatment	0.3 mg/kg	PO	Every 24 h	Assess gastrointestinal and renal tolerance; not a general substitute for an approved feline NSAID.
Alternative fixed feline regimen	1 mg/animal	PO	Every 24 h	Up to 7 days; Alternative commonly listed total amount; do not administer in addition to the mg/kg regimen. For the pain course, maximum 7 days; not an unlimited oncology prescription.
Urothelial carcinoma adjunct	0.3 mg/kg	PO	Every 24–72 h	Empirical oncology regimen; monitor GI signs, hematocrit and renal function. Alternatives are separate courses, not concurrent dosing.
Alternative neoplasia adjunct	0.3 mg/kg	PO	Every 24–48 h	Reported neoplasia course; analgesic effectiveness cannot be assumed from the cancer literature.
Cancer pain	0.3 mg/kg	PO	Every 24–48 h	Up to 7 days
Chronic idiopathic rhinosinusitis adjunct	0.3 mg/kg	PO	Every 24–48 h

Horses

Use / stage	Dose	Route	Schedule	Instructions
Experimental single exposure	Reference only	PO		A single 0.2 mg/kg oral exposure was reported without adverse effects; evidence is insufficient to recommend a treatment regimen.
Squamous-cell carcinoma case reports	Reference only	PO		Two reports used 80 mg total orally once daily after or during tumor management. One horse developed colic and was reduced to every other or every third day. These patient-specific totals are not universal equine doses.

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Fracture-associated limb swelling	0.1–0.2 mg/kg	PO	Every 8 h	Up to 21 days; Historical regimen; assess GI and renal risk.

Indications

Treatment or palliative management of selected canine urothelial carcinoma, alone or within an oncology protocol.
Adjunctive treatment of selected canine squamous cell carcinoma or other supported tumor-specific protocols, with variable disease-specific response.
Treatment of selected inflammatory musculoskeletal pain in veterinary patients when piroxicam is the chosen anti-inflammatory agent.

Contraindications

Gastrointestinal ulceration
Pregnancy
Clinically significant dehydration or renal compromise

Interactions

Do not combine with other NSAIDs or corticosteroids.
Cisplatin and other nephrotoxic drugs increase renal risk.
May interfere with diuretics and ACE inhibitors.
Anticoagulants increase bleeding risk; methotrexate toxicity may be potentiated.
Bisphosphonates may add GI ulcer risk.

Adverse effects

Vomiting or gastrointestinal ulceration
Gastrointestinal bleeding
Renal injury
Rare severe cutaneous reactions

Toxicity

Overdose can cause prolonged gastrointestinal and renal injury. Stop treatment and provide appropriate monitoring and support.

Preparations

Preparation	Form	Strength	Route
Piroxicam capsules 10 mg May require professional reformulation for accurate small-animal administration; no assumed compounded stability.	Capsule	10 mg / capsule	PO
Piroxicam capsules 20 mg	Capsule	20 mg / capsule	PO

Monitoring and Administration

Monitor appetite, vomiting, melena, CBC when bleeding is suspected, and renal function.

Dog cancer regimens may start daily and move to every 48 hours to improve tolerability; do not combine stages as concurrent doses.

The human capsule strength may be unsuitable for small animals. Compounded products need an established stability period; protect from light.

Selected canine oncology combinations retain their own protocols: piroxicam 0.3 mg/kg PO daily with alternating 3-week etoposide (50 mg/m² daily) and cyclophosphamide (12.5–25 mg/m² daily) courses for stage-II splenic hemangiosarcoma; or with mitoxantrone 5 mg/m² IV every 3 weeks for 4 treatments after urothelial tumor laser ablation. These are complex oncology plans, not simple calculator regimens.

A separate metronomic soft-tissue sarcoma course uses piroxicam 0.3 mg/kg PO daily with cyclophosphamide 10 mg/m² PO daily; alternate-day dosing was used for unacceptable adverse effects. Do not confuse mg/m² with mg/kg.

Give with food to reduce GI upset where appropriate. Some poorly tolerant dogs have been given misoprostol 3 mcg/kg PO q8h; stop piroxicam for significant ulceration or bleeding. Monitor CBC/hematocrit, liver and renal function with chronic therapy.

Piroxicam may interfere with glucose oxidase/peroxidase assays using ABTS. Product-specific compounded stability must be verified; one formulation’s 10-day period does not validate all oral mixtures.