Page 1462 - Clinical Small Animal Internal Medicine

1400 Section 12 Skin and Ear Diseases

(containing eicosapentaenoic acid [EPA] and docosahex- HCl, diphenhydramine, hydroxyzine HCl or pamoate,
VetBooks.ir aenoic acid [DHA]) are usually recommended for inflam- chlorpheniramine maleate, and doxepin HCl. Their sed-
ative effect can be beneficial when treating pruritic skin
matory conditions such as allergic skin diseases, while
omega‐6 or omega‐3/omega‐6 combination products
mines such as fexofenadine HCl and cetirizine HCl pre-
are typically recommended for keratinization disorders disorders. Although the newer generation antihista-
or to improve the skin barrier. There is no current sent a more convenient once‐daily dosage, there is no
evidence of the ideal formulation, combination, dosage current evidence that these antihistamines have superior
or ratio of essential fatty acids and many different formu- efficacy compared to the older generation antihista-
lations are available. It may take 8–12 weeks for full mines. However, their less sedative effect may be a disad-
clinical benefit to be seen. vantage for the treatment of pruritic skin disorders. A
Pentoxifylline is a methylxanthine derivative with novel anti-IL31 monoclonal antibody therapy, labeled
important anti–inflammatory and rheologic properties for the treatment of canine atopic dermatitis, is available
which results in increased red blood cell pliability, an for subcutaneous administration, under veterinarian
especially important feature for the treatment of ischemic supervision, with 4–8 weeks of efficacy duration.
dermatopathies such as vasculitis. It may be used as an
adjunctive or single agent for the treatment of various Immunosuppressive Agents
dermatoses including vaccine‐induced dermatopathies,
canine familial dermatomyositis, symmetric onychodys- Topical immunosuppressive agents include tacrolimus
trophy, cutaneous vasculitis, and various sterile inflam- and glucocorticoids (previously discussed). Tacrolimus is
matory skin diseases. It may take 4–6 weeks for clinical a calcineurin inhibitor similar to ciclosporin; however, it is
improvement to be seen. available as an ointment and is 100% more potent. It may
Combinations of a tetracycline and niacinamide have be beneficial as adjunct therapy for allergic skin diseases,
been used to treat a number of immune‐mediated discoid lupus erythematosus, pemphigus erythematosus,
diseases such as discoid lupus erythematosus, pemphi- localized cutaneous vasculopathies, and perianal fistula.
gus foliaceus, symmetric onychodystrophy, and sterile Systemic immunosuppressive agents are commonly
granulomatous diseases with variable response and a lag used for the management of immune‐mediated skin
period for efficacy of 4–6 weeks. diseases including autoimmune diseases, such as the
pemphigus complex, cutaneous bullous diseases, and
various forms of cutaneous lupus erythematosus. These
Antipruritic Agents
medications include azathioprine, chlorambucil and
Topical antipruritic substances can provide temporary cyclophosphamide, in addition to glucocorticoids and
relief and soothing effect for itching and also pain (e.g., cyclosporine (previously discussed).
lidocaine), and may be used for adjunctive treatment of Azathioprine is a derivative of 6‐mercaptopurine and
localized skin conditions including minor skin irrita- is commonly used in conjunction with a glucocorticoid
tions, allergic or pruritic reactions, acute moist dermati- for the first weeks or months as there is a lag period of up
tis, intertrigo, and acral lick dermatitis. These agents to six weeks before its effect can be noted. The use of
include colloidal oatmeal, diphenhydramine hydrochlo- azathioprine in cats is not recommended because cats
ride (HCl), lidocaine, neutralized zinc and pramox- are very susceptible to bone marrow suppression when
ine HCl, and glucocorticoids (previously discussed). treated with azathioprine.
Depending on the product, they are available as powders, Chlorambucil and cyclophosphamide are alkylating
solutions, shampoos, lotions, conditioners, rinses, sprays, agents that are more commonly used individually or in
gels, ointments, and creams. conjunction with other drugs such as glucocorticoids.
Systemic antipruritic medications commonly used Their lag period for efficacy is usually up to eight weeks.
include antihistamines and glucocorticoids (previously
discussed). Antihistamines are usually indicated for the Antibacterial Agents
management of histamine‐mediated pruritic and allergic
skin diseases including urticaria and insect bite hyper- Topical antibacterial agents are often used to treat local-
sensitivity. Despite the frequent use of antihistamines to ized bacterial skin infections such as those associated
treat atopic dermatitis, currently there is no conclusive with wounds, acne, perianal dermatitis, pododermatitis,
evidence of the efficacy of type 1 antihistamines allergic skin diseases, acral lick dermatitis, and otitis
for treatment of chronic and acute flares of canine atopic externa. They can also be a good adjunct to systemic
dermatitis. The response to any selected antihista- therapy in severe or generalized cases of bacterial skin
mine is generally individualized and unpredictable. infection. These agents include acetic acid, boric acid,
Commonly used antihistamines include amitriptyline bacitracin, benzoyl peroxide, clindamycin, gentamicin,