DERMATOLOGY
majority of allergic dogs. Few, if any, owners would
find that acceptable for their itchy dog, especially as
other safe and efficacious treatments are available. Aren’t antihistamines more convenient
than other options because they are readily
available OTC?
Are antihistamines a good first choice for dogs
that have early, mild disease? NO. When dogs have pruritus, they should always be
evaluated by the veterinarian to determine the
underlying cause, such as allergies, infections or
parasites. The danger of OTC therapies — wrong
formula (contains pseudoephedrine), wrong size,
wrong dose, wrong dosing interval — can lead to
failure or worse, including adverse reactions. Placing
treatment decisions for allergic dogs in the hands
of owners without veterinary care is very unlikely to
result in satisfactory outcomes. By suggesting OTC
medications, veterinarians set owners up for failure
and disappointment.
NO. The ability of the veterinarian to manage itch
quickly and effectively the first time a dog is presented
with allergies has important consequences for
follow-up thereafter. If early interventions fail, disease
continues, increasing the likelihood for infections
to take hold that will require antimicrobial therapy
systemically and topically.
Why put patients at risk for the additional burden
of this common complication? Many allergic dogs
have progressive, life-long disease — 7 out of 10
dogs with acute pruritus eventually require long-
term seasonal/chronic treatment. 15 Failing to provide
effective relief the first time likely causes mistrust and
lack of confidence, which decreases the likelihood
for acceptance of later recommendations. An op-ed
article by Marty Becker, DVM, in Veterinary Practice
News addresses the repercussions associated with
the failure of antihistamines to relieve pruritus and
includes: 16
• Cheapening the perception of veterinary
medicine
• Damage to the pet, pet owner, practitioner,
practice and profession by not recommending
the best FDA-approved veterinary pharmaceutical
• Pet suffers unnecessarily
• Pet owner is saddened by their dog’s continued
misery
• Loss of faith in the practice as a problem solver
• Practice loses present and future income
• The profession is tarnished
Are antihistamines inexpensive?
NO. While the cost of the actual tablets or capsules
may be low, the cost of failure (e.g., secondary
infections, loss of confidence in the veterinarian,
seeking a second opinion, loss of future business and
revenue) far exceeds the cost of effective therapies.
Is it true that antihistamines do no harm?
NO. In a comprehensive review, 12 adverse effects of
antihistamines in dogs were summarized as
the following: “Possible adverse effects listed in
textbooks and non-refereed meeting notes include
sedation, anticholinergic effects, trembling, ataxia,
hyperesthesia, hypersalivation, increased pruritus,
panting, and excitation. In addition, cardiac effects of
concern in humans (such as prolonged QT interval)
with non-sedating antihistamines also occur in
dogs; in fact, the dog has been used as an animal
model to study such effects.” This would not qualify
antihistamines as harmless.
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Issue 05 | NOVEMBER 2018 | 14
Is there any place for antihistamines
in atopic dermatitis?
POSSIBLY — IN COMBINATION WITH STEROIDS.
The ICADA guidelines 2 state: “Interventions are likely
to be of little or no benefit to treat chronic canine AD:
Type 1 antihistamines have modest efficacy against
pruritus, either alone or in combination with each
other, but their effect appears to be variable between
individuals. For optimal efficacy, this class of drugs
is best used as preventatives before a flare occurs —
not during or after it — and they should preferably be
given on a continuous daily basis.”
Thus, at best, antihistamines may be helpful when
used chronically long-term and continuously to
prevent possible disease flares. This has not been
studied, and it would seem extremely unlikely that
owners would continue oral therapy multiple times a
day continuously. One study found that the dose of
steroids used to control pruritus could be reduced by
30 percent in 75 percent of dogs when a combination
of trimeprazine and prednisolone was administered
compared to steroids alone. 17
What is the cost of treatment failure?
ENORMOUS. One study showed the factors having
the most impact on pet owners of dogs with skin
disease were emotional distress, physical exhaustion,
expenditure, and time loss. 18 Client comments
express the damage that chronic allergies have on the
human-animal bond: “Hopeless,” “Frustrating,” “I feel
like a bad mom,” “Stinky,” “Sleepless,” “Expensive,” “He
hates the e-collar” and “It’s sad that my 4-month-old
daughter sleeps longer through the night than my
dog.” Why prescribe antihistamines that will contribute
to these feelings? Dr. Becker states, “Human doctors
prescribe the best pharmaceuticals and health care
products available regardless of price. Not only does
this typically offer the best chance of an effective
treatment or cure, it keeps the human patient looking
to the family doctor for health care solutions. The
patient skips Dr. Google and aisle upon aisle or page