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Piroxicam is an NSAID that is used in the treatment of some cancers in dogs and cats, and to a lesser degree for pain due to osteoarthritis. Piroxicam is a nonselective cyclo-oxygenase (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 is also some research that COX-1 over-expression plays a role in as many as 39 percent of canine TCC incidences. Although the mechanism of action is not completely understood, COX-2 inhibitors may affect tumor cell apoptosis and disrupt tumor angiogenesis.
Like other NSAIDs, piroxicam has anti-inflammatory,
analgesic and antipyretic activity. It is less commonly used as a classic
NSAID for pain relief because there are other drugs with fewer side effects.
Piroxicam is used within a variety of protocols for the treatment of TCC, squamous cell carcinoma (oral and cutaneous), hemangiosarcoma, prostatic carcinoma and some rectal neoplasms. Many protocols combine piroxicam with a chemotherapeutic drug such as cisplatin or mitoxantrone. In one study of dogs with TCC of the bladder, 35.4 percent had a measurable response to combined chemotherapy and piroxicam, while 75 percent 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 may 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 percent response rate and a MST of almost eight months. There are additional concerns regarding renal toxicity with the drug combination of cisplatin and piroxicam (as high as 86 percent in one study). The use of piroxicam suppositories for palliative treatment of rectal cancer in dogs is well accepted for the improvement of quality of life. Piroxicam does not appear to confer additional benefits when combined with doxorubicin for the treatment of lymphoma.
Piroxicam is used in cats as an adjunctive therapy for the treatment of 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 primarily excreted
in the urine and only about 1 percent of the plasma level is found in
milk. Piroxicam may be combined with opioid analgesic drugs for the management
of pain in cancer patients. NSAIDs provide synergistic pain relief with
opioid analgesics allowing for a lower dose which may minimize the sedating
side effects.
• Side effects may include gastrointestinal irritation
and ulceration and nephrotoxicity.
• 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 may be warranted.
• Based on studies in humans, it should be used with additional 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.
• Aminoglycoside antibiotics, cisplatin may increase the risk of
renal toxicity.
• Aspirin, corticosteroids, biphosphonates may increase the risk
of GI ulceration.
• Aspirin, anticoagulants may increase the risk of bleeding.
• Piroxicam is highly protein bound and may affect the serum levels
or duration of action of other highly protein bound drugs including phenytoin,
valproic acid, oral antacids, salicylates, sulfonamides and sulfonylurea
antidiabetic compounds.
• Piroxicam may decrease the effects of furosemide.
• Methotrexate should not be combined with piroxicam due to potential
severe toxicity.
• If the overdose is recognized promptly, GI emptying with emetics and activated charcoal is warranted. GI protectants to protect against GI ulceration and fluid diuresis for renal protection may also be appropriate.
Dr.
Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania.
She has a master's degree in animal science from the University of Delaware
and graduated from the University of Pennsylvania School of Veterinary Medicine
in 1982.
She began to develop her interest in client education and medical writing 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at www.exclusivelyequine.com
The information contained on this site
is general in nature and is intended for use as an informational aid. It does
not cover all possible uses, actions, precautions, side effects, or interactions
of the products shown, nor is the information intended as medical advice or
diagnosis for individual health problems or for making an evaluation as to the
risks and benefits of using a particular product. You should consult your doctor
about diagnosis and treatment of any health problems. Information and statements
have not been evaluated by the Food and Drug Administration ("FDA"),
nor has the FDA approved the products to diagnose, cure or prevent disease.
Wedgewood compounded veterinary medicines are not intended for use in food and food-producing animals.
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