Dr. Spiegel welcomes dermatology questions from veterinarians and veterinary technicians.
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What is your treatment of choice for atopy if clients won't perform allergy testing to identify an immunotherapy formulation?
Management of atopic dermatitis often involves a multimodal approach. Treating secondary bacterial and yeast (Malassezia species) infections is the key to successful management. Preventing flea infestations and ruling out sarcoptic mange, demodicosis, and cheyletiellosis are also necessary. Addressing a potential cutaneous adverse food reaction is important as well, since a patient may be food allergic as well as environmentally allergic. Tests for food allergies are available too. However, in my experience, clients are better served by performing an elimination diet trial with a novel protein or hydrolyzed diet.
Cyclosporine is an excellent option for managing atopic dermatitis with or without immunotherapy. However, when allergy testing is not elected by the owner because of reluctance to follow-up with the required hyposensitization injections, cyclosporine is the treatment of choice.
Atopica (Novartis Animal Health) is the first oral nonsteroidal treatment approved for treating canine atopic dermatitis and, just recently, feline allergic dermatitis. Atopica is a fat-soluble, cyclic polypeptide fungal metabolite with immunomodulating activity and is a calcineurin inhibitor. Cyclosporine targets specific cells (T cells) in the immune system that lead to an allergic reaction. This is well-tolerated and highly effective when used properly. This medication lacks major adverse effects often associated with corticosteroids.
It is imperative that infections and parasites be well-controlled and treated before treatment with cyclosporine. Also, using the correct dose (5 mg/kg/day for dogs and 7 mg/kg/day for cats given orally) is important. Ideally, the modified formulation (e.g. Atopica) is a better choice, as the bioavailability is better understood, and less medication is used to achieve the desired effect.
Antihistamines may be considered, and you have several options. Some of the older-generation antihistamines such as hydroxyzine and diphenhydramine are sedating, which may prove beneficial. Other newer-generation options such as cetirizine, loratadine, and fexofenadine may be indicated. Sometimes I recommend a nonsedating antihistamine in the morning and a sedating antihistamine in the evening. While in my experience antihistamines are about 10% to 30% effective, they are still often indicated as an adjunctive treatment.
ESSENTIAL FATTY ACIDS
Essential fatty acids supplemented daily can be helpful as well. Omega-3 essential fatty acids such as eicosapentaenoic acid and docosahexaenoic acid, as well as the omega-6 essential fatty acid dihomo-gamma-linolenic acid, can decrease skin inflammation via competition with arachidonic acid for metabolic enzymes. Essential fatty acids can also modulate leukotriene and prostaglandin synthesis. Eicosanoids are anti-inflammatory. The goal is a decrease in the highly inflammatory (arachidonic acid-derived) eicosanoids (inflammatory mediators) and, thus, an increase in the less inflammatory mediators. Also, essential fatty acids help restore normal composition of lipids to skin (barrier function) and modulate lymphocyte functions.
Corticosteroids are usually indicated at some point during the management of allergies. Ideally, corticosteroids are used only when necessary and as infrequently as possible. Oral administration is, in my opinion, a better option. It allows for methodical dosage adjustments. Long-acting injection options are less ideal, in my opinion.
I usually use oral prednisolone, methylprednisolone, dexamethasone, or triamcinolone. Trimeprazine with prednisolone (Temaril-P—Pfizer Animal Health) is also an option.
In addition to the aforementioned oral medication options and injectable immunotherapy, topical treatments are helpful. Some topical antimicrobials target the secondary infections. More recently, products are available that help maintain better barrier function (e.g. Allerderm Spot-On Skin Lipid Complex—Virbac Animal Health; DOUXO—Sogeval), which is often compromised in allergic patients. There are also numerous topical anti-inflammatory and antipruritic options (e.g. corticosteroid sprays or analgesic sprays containing pramoxine). Topical treatments often compliment the other options mentioned above. In some cases, topical treatments are all that is indicated.
TYROSINE KINASE INHIBITORS
More recently, tyrosine kinase inhibitors such as masitinib (Kinavet-CA1—AB Science), which are used to treat mast cell tumors in dogs, have been considered as an option for managing allergies in dogs. Treatment with tyrosine kinase inhibitors is in the early stages, and more time will be necessary to determine how effective and safe these medications are in allergic patients.
Many management options are available for atopic patients that are not receiving allergen-specific immunotherapy. Every patient is different, and every client situation is unique. This is where the art of managing the allergic patient, and trying different options, comes into play.
And new options for treating atopic dermatitis are on the horizon. Researchers are currently investigating oral immunotherapy (sublingual) as well as regionally specific immunotherapy (formulating immunotherapy based on the most common allergens in a specific region rather than based on allergy test results).
Numerous other options are beyond the scope of this overview, but I strongly recommend reading Olivry T, DeBoer DJ, Favrot C, et al. Treatment of canine atopic dermatitis: 2010 clinical practice guidelines from the International Task Force on Canine Atopic Dermatitis. Vet Dermatol 2010;21(3):233-248.
Ian B. Spiegel, VMD, MHS, DACVD
Veterinary Specialty and Emergency Center (VSEC)
24 hr Emergency and Referral Hospital
301 Veterans Hwy, Levittown, PA 19056
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