What's new in dermatologic disease: Drugs and pathogenesis of canine atopic dermatitis - DVM
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What's new in dermatologic disease: Drugs and pathogenesis of canine atopic dermatitis


DVM InFocus


Generalized demodecosis

New treatment regimens for generalized demodicosis are being evaluated, and it appears that we may have some alternatives to the FDA-approved treatment of amitraz dipping. We also have the extralabel options of high-dose daily or every other day options of ivermectin, moxidectin, or milbemycin. Ivermectin, and to some degree moxidectin, have the greater risk of adverse reactions in certain dogs, especially dogs homozygous for the multidrug-resistant gene. Milbemycin has less risk for those reactions, but is very expensive to use in the United States at the recommended dosages.


Figures 2, 3, 4: Pre-treatment photos of a dog with generalized demodectic mange taken prior to the first treatment with a topical spot-on formulation containing amitraz. (ILLUSTRATION: USED WITH PERMISSION FROM PFIZER ATLAS OF INFECTION IN DOGS AND CATS GRIFFIN, BROWN, SMITH AND KING PUBLISHED BY THE GLOYD GROUP, INC, WILMINGTON DE COPYRIGHT PFIZER 2008, P 9-21; PHOTOS: COPYRIGHT CEGRIFFIN)
A recently approved treatment is a spot-on formulation containing metaflumizone plus amitraz (ProMeris® for dogs, Fort Dodge Animal Health). The initial report showed that twice-monthly treatment with the standard dose recommended for once-monthly flea and tick control resulted in 62.5 percent of eight dogs having a negative skin scrape by day 84. Long-term follow up and response to longer treatment was not reported. A study about the preliminary response with ProMeris® for dogs in 24 dogs with generalized demodicosis was presented by Rosenkrantz at the Western Veterinary Conference and will be published in the proceedings of the North American Veterinary Dermatology Forum, to be held in Savannah, Ga., April 15-18, 2009. In this study, 24 cases of generalized demodicosis—13 juvenile-onset and 11 adult-onset—were treated. Treatment was every two weeks with the recommended monthly dose for 90 to 180 days. Excellent results were defined as two consecutive negative scrapings, one month apart. Of the 13 juvenile onset cases, 12 of 13 (92.3 percent) had excellent results and 5 of 11 (45.4 percent) adult onset cases had excellent results. Side effects included a pemphigus foliaceus-like pustular eruption (n=1), vomiting (n=1), diarrhea (n=2), transient lethargy (n=2), and product odor (n=7). This study has not been completed regarding long-term evaluation of cure rates, but the results are encouraging and it appears we may have an FDA-approved alternative method of treating cases of generalized demodicosis. One of the cases in this study had numerous live mites, eggs and larvae on day 1. (See Figures 2,3,4) After the third visit, or 60 days after starting therapy and after five treatments, the first negative skin scrape was seen. At the 90-day recheck, the dog had its second negative skin scrape and an excellent clinical response. (See Figures 5,6,7)


Figures 5, 6, 7: Day 90 following initiation of therapy with topical spot on amitraz applied every two weeks.
Two European studies evaluated the extralabel use of a topical spot-on application of moxidectin. The product used was 10 percent moxidectin and 2.5 percent imidacloprid [Advocate® (Bayer HealthCare AG)]. One study presented only preliminary results of a single blinded protocol. The study looked at four groups, one of which was given ivermectin by mouth daily, while the others were all weekly, every other week or monthly topical applications of Advocate. The early results showed ivermectin and weekly Advocate to be more effective than other protocols. Though not statistically significant, ivermectin was showing the best results.

The second study using Advocate looked at efficacy of biweekly treatment of adult-onset or juvenile-onset generalized demodectic mange. Sixty dogs completed the study, with 26 going into remission. Response was best in dogs with milder lesions at initiation and juvenile-onset cases, as only three of 20 adult-onset cases went into remission. Based on these studies, it appears this may also be a simpler treatment option than amitraz dips, though possible weekly treatment will be preferred and milder cases may be better candidates.


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