Multimodal treatment of atopic Dermatitis

Glucocorticoids are anti-inflammatory and immunosuppressive drugs (according to the dose) that have high efficacy and rapid effect in controlling skin inflammation, pruritus and associated lesions. They can be used in dogs and cats.
For atopic dermatitis treatment, low ant-iinflammatory doses of oral corticosteroids are enough. Do not use high doses or delayed effect glucocorticoids as they are not more  effective but increase the risk of side effects.
The dosage of glucocorticoids depends on their potency. Commonly used are prednisolone and prednisone. Rarely, oral triamcinolone or oral dexamethasone are used. Dexamethasone is ten times more potent than prednisolone/prednisone, so its dose is ten times lower. Side effects of glucocorticoids are proportional to drug potency, dosage and duration of administration.

Oclacitinib (Apoquel®) is an inhibitor of IL-31, the main cytokine involved in the mechanism of pruritus, by binding and blocking its receptor Janus kinase. Oclacitinib reduces inflammation and pruritus. Its effect is fast and last a maximum of 24 hours.

It is not licensed for use in cats, but there is good scientific evidence of its efficacy at a dose of 1 mg/kg every 12 or 24 hours. Its off-label use needs close monitoring of these animals.

Lokivetmab (Cytopoint®) is a caninized anti-L31 monoclonal antibody (MAb) that specifically binds to and neutralizes IL31. It is administered subcutaneously at a dose of 1-2 mg/kg and lasts for an average of 4 weeks. It has a rapid anti-pruritic effect, generally within 8 hours of its administration. As it is a species-specific MAb, it can only be used in dogs.

Cyclosporin (CsA) is an immunomodulatory, anti-pruritic, and anti-inflammatory drug. It has no immediate effect and may take up to a month to effectively control atopic  dermatitis. Its most frequent side effects are gastrointestinal disorders that are normally temporary. The administration of the capsules frozen usually avoid these effects.

It is registered for cats and dogs. It is administered daily until effect, usually one month, and subsequently, the administration schedule is prolonged (alternate days -> 3-2 days per week).

Others

Today, it is known that histamine has no principal role as a mediator of pruritus in animals with atopic dermatitis. Scientific evidence shows that the efficacy of antihistamines for the treatment of AD is nil to moderate, being even less as monotherapy.

Topical treatment

Atopic dermatitis clinical picture appears differently in each animal. Individuality makes each individual have areas (ears, paws, axilla, abdomen, neck, inguinal region…) where inflammation and pruritus are more intense and flare easier. Topical treatment complements systemic treatment to control the most sensitive areas and is very useful as  reactive and proactive therapy. Glucocorticoids and topical tacrolimus are effective in controlling localised puritus. The recommended glucocorticoid is hydrocortisone aceponate, as it is metabolised in the skin and has no systemic effects. Other glucocorticoids can contribute to the development of iatrogenic Cushing and skin atrophy.

3. Restructuring and hydration of the skin

Changes in the skin and the cutaneous barrier have been demonstrated in atopic animals. They are due to genetic factors associated with disease and to the inflammation. Skin changes favour the multiplication of infectious agents (bacteria and yeasts), the penetration of allergens, pruritus and predispose to the development of more skin lesions.

Topical treatment focused on restoring the skin physiology and function is crucial in atopic animals.

Shampoo therapy removes allergens deposited on the skin or hair, as well as scabs, cellular debris, secretions and bacterial agents; it helps skin restructuring and hydration and has a calming, anti-inflammatory and antipruritic effect.

In addition to baths, there are products in the form of foams, creams or spot-ons with restructuring properties.

A complete and balanced diet with nutritional complexes adapted to atopic disease is also necessary.

4. Secondary infections control

Secondary bacterial (pyoderma) or Malassezia infections are very common in atopic animals. Skin infection causes puritus and increases inflammation. Puritus due to infection is not controlled with antipruritic drugs.

In any atopic animal with active lesions, the possible existence of an infectious component must be evaluated and, if necessary, treated.

5. Allergen-specific immunotherapy (ASIT)

It is the only treatment that can reverse this incurable disease. It is a long-term treatment whose objective is to “educate” the immune system not to overreact to environmental allergens. Its use is recommended in all animals diagnosed with atopic dermatitis.

ASIT does not have an immediate effect, as “education” of the immune system takes time, and should be joined to the antipruritic treatment until maximal effect. Some animals can have an excellent response in 4-6 months, but the maximum response to ASIT can take 1-2 years in other cases. A recent study describes an improvement in the clinical picture in a mean time of 4.7 months. 58% of dogs were maintained exclusively with ASIT, without the need for additional medication, in less than ten months of the start of treatment.

It should be used together with antipruritic treatment until possible to reduce or suspend antipruritic treatment (better efficacy after one year of treatment).

Dr Carmen Lorente, DVM, PhD, DipECVD EBVS® European Specialist in Veterinary Dermatology