Canine atopic dermatitis is one of the most common allergic skin diseases of dogs. Depending on the severity of clinical signs and whether the dog has seasonal or year-round allergies, various treatment strategies can be used. Glucocorticosteroids have long been considered the gold standard against which both owners and veterinarians measure the efficacy of control of pruritus. However, long-term and/or sole use of steroids is problematic because of their adverse effects. Cyclosporine A (CsA), a polypeptide macrolide originally developed to prevent organ rejection in human transplant patients, is the newest drug for the management of pruritus due to atopy. Fifty-one dogs with atopic dermatitis were treated with CsA for at least 6 months (6 to 30 months) at a dose of 5 mg/kg PO per day. When the medical records of these dogs were retrospectively examined, the authors found that 28 (55%) continued to receive the drug anywhere from 1 to 3 times a day. In 23 dogs (45%), CsA was discontinued after 6 to 24 months of therapy for a variety or reasons. Twelve dogs achieved clinical remission for 3 to 22 months after discontinuation of the drug. Of these 12, 9 did not require further treatment, and 3 became pruritic after developing secondary bacterial/yeast infections. These dogs became asymptomatic after antimicrobial therapy. The drug was discontinued in 6 of the remaining 11 dogs due to inadequate benefit in the owner's assessment and in 5 dogs due to cost. Thirteen of 51 dogs had elevated liver enzymes, cholesterol, or glucose, or hypoalbuminemia. Two dogs developed oral growths, and 1 developed hirsutism. Most owners (71%) reported being satisfied with the treatment, and few (22%) reported adverse effects.

COMMENTARY: This study answers many of the common questions clients ask when they are considering CsA therapy. Based on the findings, the drug seems to be well tolerated in most dogs, has relatively few adverse effects, and can be used safely for long periods. What was most interesting was that 12 of 51 dogs responded so well that the clinician and owners agreed to discontinue the medication. A problem-free clinical remission was maintained in 9 of these12 dogs. However, clients should be warned that adverse drug effects, such as vomiting, diarrhea, inappetence/lethargy, gingival hyperplasia, and oral papillomas, can develop.

Long-term use of cyclosporine in the treatment of canine atopic dermatitis. Radowicz SN, Power HT. VET DERMATOL 16:81-86, 2005.