Its not magic: The skinny on treating canine atopic dermatitis

Canine atopic dermatitis is like a trickster in a fairy tale-always causing chaos. But let's talk about a more practical kind of magic. After all, you don't need to be Houdini to get pet owners to cheer for your successful treatment of their itchy pets. It is true that an estimated 10% to 15% of dogs suffer from atopic dermatitis; and the actual number is probably considerably higher. Atopic dermatitis typically manifests as pruritus and erythema, but some dogs develop recurrent pyoderma or otitis externa instead. Here's how to take the intrigue out of canine atopic dermatitis-no secret key or sleight of hand required.

We're talking about a long-term relationship here!

In his CVC presentation, Dr. Darin Dell explained the importance of a supportive relationship with owners of atopic dogs and of asking what they can handle-you're in it for the long haul! Hear it here:

No magic pill

No single therapy is 100% effective at treating atopic dermatitis. Most patients need a core therapy and one or two supportive therapies. Four core allergy therapies that are safe for long-term use are 1) immunotherapy, 2) cyclosporine, 3) oclacitinib and 4) canine atopic dermatitis immunotherapeutic (CADI).

Immunotherapy

Immunotherapy, the gold standard of allergy therapy, is the only treatment that changes the immune system's response to allergies rather than suppressing the immune system or dulling the clinical signs. Immunotherapy can prevent new allergies from developing. It is also the only therapy that could potentially cure a patient. However, the cure rate is low, and most dogs require immunotherapy for life.1

Onset of action: Six to 12 months for significant benefit

Side effects: No major side effects (anaphylaxis can occur but is rare)

Tips

Both administration routes (subcutaneous injections and sublingual drops) are effective. The best choice is the one that the owner will comply with.

Because of the slow onset of action, many patients need an additional core therapy when beginning immunotherapy.

Dogs should receive immunotherapy for a year before you and the owner discuss whether it is worth continuing.

Cyclosporine

Cyclosporine (Atopica-Elanco) treats allergy signs by suppressing IL-2, T helper cells, and T suppressor cells.2

Onset of action: Four to six weeks for full effect

Side effects: Mild vomiting and diarrhea are the most common. Hypertrichosis, gingival hyperplasia or immunosuppression is possible.

Tips

To help prevent vomiting, owners can freeze capsules, give the medication with a small meal, divide the dose throughout the day, or start with a low dose and ramp up to the target dose over two weeks.

Since cyclosporine does not provide immediate relief. I combine it with a corticosteroid during the first two or three weeks of treatment.3

Do not taper cyclosporine until the desired response has been reached. It is best to taper slowly by eliminating one dose a week until every-other-day dosage is achieved or clinical signs relapse. If a relapse occurs, the client should return to the previously effective dosing regimen. An inability to taper does not indicate treatment failure; some dogs require daily therapy long term.

Oclacitinib

Oclacitinib (Apoquel-Zoetis) treats allergy signs by blocking IL-31-the cytokine linked to the feeling of itch-and suppressing IL-2, IL-4, IL-6 and IL-13.

Onset of action: One or two days, but some dogs improve within 30 minutes. I have had a few patients not respond for five to seven days.

Side effects: Decreased hematopoiesis and immune suppression are potential side effects, especially at higher dosages and in dogs less than 12 months of age. Published safety studies have thus far found minimal changes on hematologic tests at maintenance dosing. Vomiting and diarrhea were the most common side effects in clinical studies. 4,5 However, I have had a couple patients develop vomiting severe enough to stop the medication.

Tips

A twice-a-day dosage is recommended for the first two weeks and then once daily thereafter. I have had some patients whose skin worsened when the frequency was reduced to daily, but eventually, these dogs did get back to the desired level of relief with the daily dosage.

Calculate the low and high end of the dose range using 0.4 to 0.6 mg/kg instead of using the dosing chart provided.

Editor's note: Apoquel has been in the news-but despite shortage issues in the past, Zoetis announced it's now in fully supply. Find more coverage here.

CADI

CADI (Zoetis) is a once-a-month injection of a monoclonal antibody that targets IL-31. It is available through most veterinary dermatologists and some general practitioners.

Onset of action: One or two days, but some dogs feel itch relief as soon as 30 minutes.

Side effects: None

Tips

It is safe for puppies and dogs with other health problems.

CADI is beneficial for dogs with owners who may not see well enough to give a pill or may forget to give it every day.

We do not know what clinical effect CADI will have on allergic otitis, recurrent pyoderma or allergy-related erythema since it only targets the cytokine linked to itch.

A magical(ish) treatment strategy

Every allergen patient is different-different allergies, primary signs, and secondary problems-so every treatment needs to be different, too. Nevertheless, your treatment strategy should be consistent.

Step 1. Provide adequate flea control. Any allergy (e.g. flea, food, seasonal) can cause other allergies to get worse-it can kick start inflammation. So ensure that fleas are a nonissue by making sure these dogs are receiving appropriate flea control.

Step 2. Eliminate infections. Eliminating infections reduces pruritus and inflammation while also improving the patient's odor and appearance. Dogs with allergies may be slower to respond to antibiotics than dogs without allergies are, so check progress after three weeks of antibiotic therapy but treat until infections are gone.

Step 3. Rebuild the epidermal barrier with ceramides. When the epidermal barrier is intact, there is less allergen exposure, less risk of infection and less pruritus. You can find ceramides in shampoos, sprays, conditioners and spot-on products.

Step 4. Conscientiously choose a core treatment. First and foremost, the best treatment is the one that the owner will actually administer correctly. Beyond that, consider the patient's underlying medical conditions, the severity of the allergy, and the primary signs.

Step 5. Add supportive therapy as needed. These therapies include antibacterial and antipruritic shampoos, wipes and sprays as well as oral antihistamines, oral essential fatty acids and topical ceramides. Reevaluate your supportive therapy after a month and then on an on-going basis, as the patient's needs will likely change over time.

Editor's note: It may not be as obvious as the old rabbit out the hat, but successful treatment of atopic dermatitis can be magic for the human-animal bond. For more ideas, tools and tips, check out the dvm360 dermatology toolkit.

References

1. Dell L. Darin, Griffin CE, Thompson LA, et al. Owner assessment of therapeutic interventions for canine atopic dermatitis: a long-term retrospective analysis. Vet Dermatol 2012;23:228.

2. Guaguere E, Steffan J, Olivry T. Cyclosporin A: a new drug in the field of canine dermatology. Vet Dermatol 2004;15:61-74.

3. Dip R, Carmichael J, Letellier I, et al. Concurrent short-term use of prednisolone with cyclosporine A accelerates pruritus reduction and improvement in clinical scoring in dogs with atopic dermatitis. BMC Vet Res 2013;9:173.

4. Cosgrove SB, Wren JA, Cleaver DM, et al. A blinded, randomized, placebo-controlled trial of the efficacy and safety of the Janus kinase inhibitor oclacitinib (Apoquel) in client-owned dogs with atopic dermatitis. Vet Dermatol 2013;24,587-597.

5. Zoetis, Apoquel package insert, February 2013.

Darin Dell, DVM, DACVD

Animal Dermatology Clinic

3901 East 82nd St.

Indianapolis, IN 46240