Cyclosporine is increasingly being used in veterinary medicine to treat diseases known to be glucocorticoid responsive, the most common being atopy. There are several formulations of the drug, and the veterinary product Atopica (Novartis, www.novartis.com) is the only one approved for use in dogs. Atopica is a microemulsion that enhances absorption; bioavailability varies from 23% to 45%, and the presence of food may decrease absorption. The initial starting dose is 5 mg/kg Q 24 H. It may take 2 to 4 weeks to see a response; a 4-week minimum duration is recommended to determine whether the drug will be beneficial. Some patients can be maintained on a dosage of Q 72 H or every 4 to 7 days. Drugs that compete for the enzyme that metabolizes cyclosporine can be used to help keep serum levels high and thus decrease cost of the drug. One drug commonly used is ketoconazole given approximately 8 to 12 hours before the cyclosporine. Cyclosporine has 2 major adverse effects: diarrhea and vomiting. The concurrent administration of cyclosporine with food may prevent vomiting, and after several days the dog may be able to tolerate the drug without food. Metoclopramide, 0.2 to 1 mg/kg Q 24 H, may help control vomiting. Diarrhea can often be controlled by stopping the drug temporarily or adding metronidazole or fiber to the diet. Other common adverse effects include hirsutism, gingival hyperplasia, and bacterial infections. In cats treated with cyclosporine, toxoplasmosis has been observed. Nephrotoxicity and hepatotoxicity have not been observed in dogs. Monitoring of serum concentrations of the drug is not recommended because the target clinical sign is pruritus. Patients should be evaluated by routine physical examination every 3 and 6 months after starting therapy. At least once a year, complete blood counts, serum chemistry panels, and urinalyses are recommended.
COMMENTARY: Several generic formulations are on the market, and the high cost of Atopica will prompt many clients to bring this to your attention. When discussing this with clients, it is important to point out that cyclosporine A modified is the drug that most closely resembles Atopica. It is also important to point out that little is known about the bioavailability of generic formulations in dogs. Vomiting has been the major problem that I have encountered. In addition to metoclopramide, I have successfully used over-the-counter motion-sickness medication, which is administered the night before the cyclosporine. In my experience, the most common dosing interval is Q 24 or Q 48 H.
Cyclosporine: Making it an option for more clients. Griffin CE. PROC NAVC 2007 pp 326-328.
