Atopy therapy: minimizing drugs (or at least the immunosuppressive ones) (Proceedings)


Atopy therapy: minimizing drugs (or at least the immunosuppressive ones) (Proceedings)

Nov 01, 2010

Atopy or Atopic dermatitis continues to be one of the most common dermatological disorders afflicting both dogs and cats. At our referral dermatology specialty practice, 75% of our patients have atopic dermatitis as one of the final diagnosis. The problem is so common and severe that many drugs have been utilized in an attempt to offer relief to the suffering patient. The challenge for the clinician is to try and find the right balance between all of the drugs, their cost, efficacy and safety. The disease continues to generate research, with new therapies being developed as well. The International Task Force on Atopic Dermatitis developed guidelines in 2010 for the treatment of atopic dermatitis which involve a multifaceted approach including
     • Treatment of acute flares
     • Attempt to ID and avoid all triggers of flare
     • Improve skin & coat hygiene
     • Treat ongoing pruritus with drug therapy
     • Allergen specific immunotherapy should be offered when feasible

The diagnosis of atopic dermatitis is not based on any laboratory or skin test but is based on a combination of signalment, history, clinical signs and the ruling out other causes of inflammatory skin. Minimizing the drugs begins with a certain and complete diagnosis of all the triggers of the atopic patient.

When attempting to effectively help a patient with atopic dermatitis it is necessary to understand the pathogenesis of the disease, and teach the client these basic concepts.
     • In dogs, atopic dermatitis is known to be an inherited type 1 hypersensitivity reaction to percutaneously absorbed antigens
     • Epidermal barrier defects contribute to the pathogenesis
     • Bacterial and yeast infections provide additional antigens which exacerbate pruritus

I try and simplify options with clients and explain there are four groups of options for the treatment of atopic dermatitis. They include supportive therapy, corticosteroids, cyclosporine and allergen specific immunotherapy. The point of this lecture is how to minimize the corticosteroids and cyclosporine (C&C). Allergen specific immunotherapy is covered in more detail in a separate lecture. These options are frequently used in combination in order to obtain synergistic effects, which is an important point to teach clients. In order to use less C&C clients must administer more intensive supportive therapy.

Supportive therapy is always a good place to start when treating a "mildly" affected atopic patient and includes antihistamines, essential fatty acids, bathing, restoration of the epidermal barrier, control of secondary infections, and potentially topical anti-inflammatory products.

A number of antihistamines have been utilized to control pruritus in dogs. Good clinical trials with placebo controls show the benefits of reducing pruritus ranging from zero to 30%. Many dermatologists will utilize antihistamines as part of the ongoing maintenance control of atopic dermatitis, but recognize their limited value when treating an acute or intense flare. Antihistamines which we currently recommend at our practice include cetirizine, amitrpytilline, Clemastine, diphenhydramine, and chlorpheniramine. Most are available in generic formulation, and are over the counter, which helps keep the cost low. I usually try 2-3 different antihistamines, but expectations need to be realistic in understanding the value of these drugs may be in their steroid sparring effects. Remind owners to avoid formulas which contain decongestants and pain relief products.

There are many published reports regarding efficacy of essential fatty acids (EFAs) for the treatment of atopic dermatitis. Unfortunately many of these studies failed to control, or account for the amount of EFAs in the diet which makes interpretation and comparison of these studies difficult. Most dermatologist support the use of EFAs in the treatment of chronic atopic dermatitis. Despite claims to the contrary, currently it is the position of the Task for on Atopic Dermatitis that there is no evidence of superiority of any particular EFA combination, dosage, ratio or formulation (including enriched diets) to improve skin and coat quality. As with antihistamines, EFAs are not adequate as a single therapy for atopic dermatitis except in mildly affected patients. I recommend minimizing other oils or fats such as olive oil or animal fat to minimize competition for absorption of the EFAs.

Improvement of the epidermal barrier has recently been getting more investigation and implementation. Simply bathing the atopic patients has many benefits including
     • Physical removal of antigens
     • Reduction of bacterial and yeast populations
     • Repair epidermal barrier defects
     • Anti-pruritic effects and cooling hot inflamed skin