Piroxicam is a non-steroidal anti-inflammatory drug which has anti-inflammatory, analgesic, anti-pyretic, and anti-tumor activity. While approved for human use only, it also has some veterinary applications. Currently, its main use is as adjunctive therapy in the treatment of transitional cell carcinoma of the bladder in cats, and it is also used in dogs.
Mechanism of Action: The anti-tumor mechanism has not been determined, but, because direct tumor cell cytotoxicity has not been demonstrated, may involve modulation of the immune system.
Transitional cell carcinoma adjunctive treatment: Feline Dose : 0.3 mg/kg PO with food q 24 hours or q 48 hours (depending on tolerance and creatinine). Normal creatinine in the cat is 1; therefore, if Cr=2, then halve the frequency of administration. Note: The canine dose is 0.3 mg/kg PO q 24 hours.
Adverse Drug Reactions: GI irritation and bleeding, renal papillary necrosis, peritonitis, inhibition of platelet aggregation.
Availability: 10 mg & 20 mg capsules (human approved only).
Client information: Give drug with food to reduce GI upset potential. Monitor patient for anorexia, tarry stools, or other symptoms of GI bleeding.
Comments: Because piroxicam is a human approved drug, the commercially available strengths are unsuitable for cats. For example, the average cat requires a dose of 1 to 2 mg piroxicam. A compounding pharmacist can reformulate the capsules into a manageable dosage form (either capsules, chewables, or oral suspensions) in order to meet individual patient needs. Some published data indicate that oral compounded suspensions retain their potency less than a week (Trissel’s Stability of Compounded Products). Other anecdotal reports indicate that compounded suspensions of piroxicam maybe stable for up to 4 weeks depending upon formula and vehicle.
Note: There is an excellent educational article on bladder tumors in dogs and cats in the June, 1999 edition of the Compendium on Continuing Education for the Practicing Veterinarian, pp 540-546.
References: Plumb, Donald C. Veterinary Drug Handbook, 3rd edition. Ames: Iowa State University Press, 1999.