Dr. Fan welcomes oncology questions from veterinarians and veterinary technicians.
E-mail: vm@advanstar.com
With the subject line: Oncology questions

Q: Does piroxicam have any effect in cats with transitional cell carcinoma of the bladder? If so, what is the recommended dosage?

A. Piroxicam is a mixed COX-1/COX-2 inhibitor that reduces the production of various inflammatory lipid mediators. Such lipid mediators, including prostaglandin E2, may favor the development and growth of tumors through various mechanisms, including the promotion of new blood vessel growth, immunosuppression, and reduced death signaling. Because of these effects, piroxicam has demonstrated modest activity in dogs with transitional cell carcinoma.¹

The potential anticancer effects of piroxicam in cats with transitional cell carcinoma have not been thoroughly described,² but, anecdotally, piroxicam appears to be well-tolerated at a dosage of 0.3 mg/kg by mouth two or three times a week.² Using this dosing scheme in cats with transitional cell carcinoma should be safe based on prior pharmacokinetic studies of oral piroxicam conducted in healthy cats^3,4; however, its anticancer effectiveness remains poorly characterized in cancer-bearing cats.

References
1. Knapp DW, Richardson RC, Chan TC, et al. Piroxicam therapy in 34 dogs with transitional cell carcinoma of the urinary bladder. J Vet Intern Med 1994;8(4):273-278.
2. Wilson HM, Chun R, Larson VS, et al. Clinical signs, treatments, and outcome in cats with transitional cell carcinoma of the urinary bladder: 20 cases (1990-2004). J Am Vet Med Assoc 2007;231(1):101-106.
3. Heeb HL, Chun R, Koch DE, et al. Single dose pharmacokinetics of piroxicam in cats. J Vet Pharmacol Ther 2003;26(4):259-263.
4. Heeb HL, Chun R, Koch DE, et al. Multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine in the cat. J Vet Pharmacol Ther 2005;28(5):447-452.  

Timothy M. Fan, DVM, PhD, DACVIM (internal medicine and oncology)
Department of Veterinary Clinical Medicine
College of Veterinary Medicine
University of Illinois
Urbana, IL 61802

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