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An Urban Experience
COX-2 inhibitors. Firocoxib (5mg/kg once daily) has been demonstrated to decrease the erythema, dermal thickening and other lesions in dogs. Other COX-2 inhibitors may also be of benefit, including topical 3% diclofenac gel (applied twice daily). The response is typically slow—some response may be noted by 60 days, but gradual improvement may continue over the next several months.
Natural or synthetic retinoids may be helpful for some lesions. Vitamin A can be given to dogs at 800-1000 U/ kg once daily with a fatty meal. Alternately, the synthetic retinoid acitretin can be given to dogs at 0.5-1mg/
kg once daily and to cats 5-10mg per cat once daily. Patients should be monitored for the development of keratoconjunctivitis sicca and hepatotoxicity. Neither vitamin A nor synthetic retinoids should be administered to pregnant females, as the teratogenic potential of these compounds is high. Topical retinoids such as tretinoin may also be helpful. However, these medications are photosensitizing and topical sunscreens should also be applied.
Topical application of imiquimod may decrease the severity of focal solar dermatitis or early squamous cell carcinoma lesions, especially in cats. The product is to be applied two to three times weekly until the lesions are resolved. Significant inflammation may be seen at the application site, at least initially.
Limitation of sun exposure:
The most critical factor in the treatment of solar dermatitis is limitation of additional sun exposure. Solar radiation is at its highest from 9AM to 3PM. Ideally, patients should be kept indoors and away from open windows or doors during that time. In addition, clients should be encouraged to minimize the time that their
pet spends sunbathing by windows. Although window glass blocks most UVB rays (minimizing the risk of acute sunburn), much of the UVA light (involved in chronic solar dermatitis) will pass through the glass.
If patients cannot be kept indoors, some benefit may be derived from keeping them in the shade. However, UVA light readily reflects from many surfaces. Sunscreen can be used to protect vulnerable areas. Products designed for dogs and cats are ideal, but may be difficult to find. Waterproof, high SPF (30+) products should be used. Sunscreens incorporating zinc should be avoided in dogs and cats, as ingestion may produce zinc toxicity. Sunscreens incorporating salicylates should be avoided in cats. Best results may be seen when the sunscreen is applied shortly before sun exposure. Reapplication may be necessary in a few hours if prolonged exposure is expected.
If sunscreen application is not possible, the use of UV- protective dog garments (, au,, others) may help protect the trunk and legs. Patients wearing these garments should be monitored to be certain that they do not overheat.
Miscellaneous therapies:
Early lesions may respond to beta carotene supplementation. Dogs may receive 30mg/kg and
cats may receive 30mg per cat. The medication is initially administered twice daily for 30 days, and once daily thereafter. Other therapies have been proposed (Vitamin E, Vitamin C, tacrolimus, topical 5 fluoruracil, pentoxifylline) but to the author’s knowledge no research has been conducted to demonstrate the benefit of these medications. Tattooing has been suggested to protect against solar exposure. However, the ink is deposited
in the in the dermis, leaving the epidermis and most superficial dermis exposed. For this reason, tattooing is unlikely to be of benefit and may actually make matters worse by concealing the progression of disease. Severe lesions or lesions that have undergone neoplastic transformation may be treated by surgical excision, cryotherapy, laser therapy or strontium irradiation.
Selected references:
1. Miller W, Griffin C, Campbell K. Muller and Kirk's Small Animal Dermatology. 7 ed. St. Louis, Missouri: Elsevier Mosby; 2013.
2. Hnilica KA. Small Animal Dermatology. 3 ed. St. Louis, Missouri: Elsevier Saunders; 2011.
3. Albanese F, Abramo F, Caporali C, Vichi G, Millanta F. Clinical outcome and cyclo-oxygenase-2 expression in five dogs with solar dermatitis/actinic keratosis treated with firocoxib. Vet Dermatol. 2013;24(6):606-12
4. Peters-Kennedy J, Scott DW, William H. Miller J. Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream. Journal of Feline Medicine and Surgery. 2008;10(6):593-9.

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