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Piroxicam for Dogs and Cats

By Evan Ware, DVM

Commonly prescribed for: Anti-neoplastic activity and pain associated with osteoarthritis

Species: Dogs and Cats

Therapeutic Class: Non-steroidal Anti-inflammatory Drug (NSAID)


Basic Information

Piroxicam is a non-steroidal anti-inflammatory (NSAID) drug belonging to the oxicam class. In humans, it's used as an analgesic, to relieve arthritis symptoms, and to ease postoperative pain.

Piroxicam is used to treat some cancers in dogs and cats and, to a lesser degree, for pain due to osteoarthritis. Piroxicam is a nonselective cyclooxygenase (COX) inhibitor with inhibitory effects on both COX-1 and COX-2. COX-1 produces prostaglandins that regulate homeostasis, allowing the kidney to respond to hypotension and protect the GI tract. COX-2 produces the prostaglandins that are increased in the presence of inflammation. COX-2 is upregulated in many types of tumors, including nasal epithelial tumors, mammary tumors, colorectal tumors, oral squamous-cell carcinoma, oral melanoma, prostatic carcinoma, transitional cell carcinoma (TCC) of the urinary bladder, and osteosarcoma.

There also is some research that COX-1 over expression plays a role in as many as 39% of canine TCC incidences. Although the mechanism of action is not understood completely, COX-2 inhibitors can affect tumor cell apoptosis and disrupt tumor angiogenesis.

Veterinary Medicine Uses for Piroxicam

In veterinary medicine, Piroxicam is most often prescribed to treat certain types of cancers, such as colon, prostate, and bladder cancer. It also can be used to treat arthritis pain, though other products generally are preferred for those purposes.

The exact mechanism by which Piroxicam combats mammary adenocarcinoma, squamous cell carcinoma, TCC, and other cancers, isn't completely understood, but its therapeutic success is well known.

In veterinary chemotherapy, Piroxicam can be used to reduce the necessary dosage of Methotrexate, a drug used to treat certain types of lymphoma. It also can be combined with opioid analgesics to reduce discomfort in oncology patients, while reducing the drowsiness commonly associated with those drugs.

In one study of dogs with TCC of the bladder, 35.4% had a measurable response to combined chemotherapy and piroxicam, while 75% showed subjective improvement. Mean survival time (MST) for dogs with TCC treated with the combination of piroxicam and mitoxantrone was just under a year. Radiation therapy can be added to piroxicam and mitoxantrone protocols for TCC.

Piroxicam is thought to have a positive effect on survival time for prostatic carcinoma (MST = 6.9 months). Treatment of oral squamous-cell carcinoma with cisplatin and piroxicam resulted in a 56% response rate and an MST of almost eight months. There are other concerns regarding renal toxicity with the drug combination of cisplatin and piroxicam (as high as 86% in one study). The use of piroxicam suppositories for palliative treatment of rectal cancer in dogs is well accepted to improve quality of life. Piroxicam does not appear to confer additional benefits when combined with doxorubicin to treat lymphoma.

Piroxicam is used in cats as an adjunctive therapy to treat TCC of the bladder and oral squamous-cell carcinoma. The half-life of piroxicam in the cat is 12 to 13 hours, which is shorter than the 37- to 40-hour half-life in dogs.

Piroxicam is well-absorbed orally and the absorption is not affected by the presence of antacids. It should be given with food to decrease the likelihood of GI ulceration. Piroxicam is excreted primarily in the urine and only about 1% of the plasma level is found in milk. Piroxicam can be combined with opioid analgesic drugs to manage pain in cancer patients. NSAIDs provide synergistic pain-relief with opioid analgesics allowing for a lower dose, which can minimize the sedating side-effects.

Potential Side-Effects of Piroxicam

Piroxicam should be used with caution in dogs with cardiac issues. It should not be given to dehydrated animals and its use can require additional hydration. GI ulceration is a potential side-effect, so animals taking Piroxicam should be monitored for symptoms such as vomiting, or loose, tarry stool. If these symptoms present, a veterinarian should be contacted immediately.

Drug Interactions with Piroxicam

As a protein-bound drug, Piroxicam can alter the effectiveness of other protein-bound medications, such as phenytoin, valproic acidoral antacids, salicylates, sulfonamides, and sulfonylurea antidiabetic compounds.

If used with aspirin or other anticoagulants, Piroxicam can increase the risk of bleeding, and can raise chances of gastrointestinal ulceration when administered in combination with bisphosphonates, aspirin, or corticosteroids. Renal toxicity can result if Piroxicam is given with cisplatin or aminoglycoside antibiotics.

Precautions for Using Piroxicam

Piroxicam has a narrow margin of safety due to GI and renal side-effects. Piroxicam should not be used in dehydrated animals and fluid supplementation can be warranted. Based on studies in humans, it should be used with more caution in dogs with decreased cardiac function.

Animals taking piroxicam for extended periods should be monitored for GI bleeding and be followed for renal and liver function.

Dosage and Administration of Piroxicam

Piroxicam is typically administered orally but is occasionally formulated for injection. If an overdose is recognized promptly, GI-emptying with emetics and activated charcoal is warranted. GI protectants against GI ulceration and fluid diuresis for renal protection also can be appropriate.

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