In atopy, because pruritus and changes in skin and coat quality (i.e., lipid changes in the epithelium) occur, I prefer to
use a product with a mixture of both omega 3 and 6 fatty acids. I find that these supplements can take several months to become
effective, so it might be a good idea to start the atopic patient off on these immediately.
One mistake that clients make is discontinuing the product after the usual 60-day supply is completed, either because the
dog is doing well or because they feel the product is not working. In either case, it needs to be explained that these supplements
may be more preventive than thera peutic, at least initially when building up to an effective level.
Some evidence shows that combining fatty acids with an antihistamine may in fact increase the rate of reducing pruritus. These
supplements can be helpful particularly in clients that want to employ "natural" and/or non-drug means to treat their pets.
Many owners administer antihistamines without first consulting veterinarians, thereby giving too low a dose. Or they may use
one of the newer antihistamines that do not yet have recommended doses.
Antihistamines in the atopic dog reportedly are successful about 10 percent to 30 percent of the time, although I have not
seen that high a success rate in my practice. However, because antihistamines are a better choice than steroids, veterinarians
continue to dispense them with the hope that they will be effective.
Some of the newer antihistamines and their doses for dogs include: Claritin 10mg tablets (loratidine) — 0.5mg/kg sid; Clemastine
1.34mg. tablets – 0.05mg/kg bid; Allegra 10mg if <10kg, 20mg if 10-14kg, 60mg if >25kg body wt. sid.
Old standbys include: hydroxyzine 1mg/lb body wt b-tid; diphenhydramine 1mg/lb body wt b-tid; chlorpheniramine 2-12mg b-tid;
amitriptyline 1-2mg/kg s-bid; doxepin 1-2mg/kg sid.
Most dermatologists believe an adequate trial is 14 days, then if not effective change to another antihistamine of a different
Antihistamines are not without side effects, and they should be used with caution in breeding dogs and those with seizures,
glaucoma and cardiac problems. Antihistamines can be helpful when used with a combination of therapy for atopy such as immunotherapy,
fatty acids and bathing.
Nothing has revolutionized therapy for atopic dogs recently more than cyclosporine. Whereas some patients that were nonresponsive
to immunotherapy or relied on steroids to maintain their condition, cyclo sporine appears to be an important alternative.
Perhaps the most important qualification for using cyclosporine is the determination that the patient is, in fact, atopic.
It sounds elementary but as always with the diagnosis of atopy, a good dermatological history is important, including age
of onset, seasonality vs. non-seasonality, breed of dog, areas of the body affected and, in some patients, response to steroids.
A diagnosis of atopy is confirmed by a good history and ruling out the other differentials of atopy, including ectoparasites,
food allergy, bacterial pyoderma, yeast dermatitis and hypothyroidism. Atopy is not confirmed by a positive serum test or
by a positive skin test because some non-atopics will test positive for allergy and 5 percent of atopics will have negative
skin and blood tests.
The main side effects we have seen with cyclosporine at 5mg/kg/day is vomiting and diarrhea, so I will start some patients
at a lower dose, particularly those with a sensitive GI tract.
In some patients that still experience vomiting on a low dose of the cyclosporine capsule, changing to cyclosporine oral liquid
(100 mg/ml) or adding Pepcid AC to the regimen may be advised. Most patients will respond in 30 to 60 days, and some patients
are able to go on an every-other-day regimen or less. Long-term effects of cyclosporine include gingival hyperplasia (usually
reversible upon discontinuation of the drug), papillomas, neutropenia and hypoalbuminemia.
When yeast accompanies atopy, lower doses of cyclosporine may be possible if ketoconazole is added to the regimen. There is
no set dose of ketoconazole that will prolong cyclosporine in each patient; it appears to be individual.