Dogs have reaction to certain drugs

DEAR DR. FOX: I have just adopted a 6-month-old female Australian shepherd mix from an adoption network. A friend warned me that this breed can get ill and die from heartworm prevention medication. I respect his advice — he is a dog trainer and seems to know a lot. What is your opinion? — K.P., Silver Spring, Md.

DEAR K.P.: First, let me say that I now endorse year-round heartworm preventive medication for most dogs. Your dog should also get periodic blood tests to check for heartworms because of climate change, traveling and the fact that more than 70 species of mosquitoes can transmit this disease. Your veterinarian can determine if it is safe to temporarily stop the monthly medication during the winter season.

You raise an important issue, which needs to be addressed. I hope all readers with dogs will take note because dogs do have adverse drug reactions, and many drugs are now being prescribed for the dogs' entire lives. Washington State University's College of Veterinary Medicine advises, "Many herding breed dogs have a genetic predisposition to adverse drug reactions involving over a dozen different drugs. The most serious adverse drug reactions involve several antiparasitic agents (ivermectin, milbemycin and related drugs), the antidiarrheal agent loperamide (Imodium), and several anticancer drugs (vincristine, doxorubicin, others). These drug sensitivities result from a mutation in the multi-drug resistance (MDR1) gene. At Washington State University's College of Veterinary Medicine you can test your dog for multi-drug sensitivity and prevent serious adverse drug reactions. We can work with your dog's veterinarian to find appropriate drug doses or alternative drugs for your dog based on results of MDR1 testing."

Consult with your veterinarian about this genetic blood test, also available from other laboratories.

The university also posted the following breed prevalence as an approximate percentage frequency of the genetic mutation causing multidrug sensitivity: Australian shepherd, 50 percent; mini Australian shepherd, 50 percent; border collie, 5 percent; Collie, 70 percent; English shepherd, 15 percent; German shepherd, 10 percent; herding breed cross 10 percent; long-haired whippet, 65 percent; McNab, 30 percent; mixed breed, 5 percent; old English sheepdog, 5 percent; Shetland sheepdog, 15 percent; silken windhound, 30 percent.

As advances are made in canine genetics and related nutrigenomics — specific dietary requirements related to genetic background — the burden of disorders and suffering related to our selective breeding of various kinds of dogs may be alleviated, and our canine companions can enjoy a better quality of life in future generations. Overall, mongrels — mixed breeds, not the new "designer" breeds — have the best prognosis.

DEAR DR. FOX: I would like to hear your rationale as to the difference between horse slaughter for human consumption, which you discussed in a recent column, and that of cattle, hogs, poultry and fish? — B.W., St Louis

DEAR B.W: My "rationale" is quite simple: While killing is killing regardless of the species, there is a difference in slaughtering animals raised or caught specifically for human consumption and those such as horses and dogs, who have enjoyed a close human bond.

This difference is cultural and, some would argue, also ethical. It is a kind of emotional betrayal of the animals' devotion and service. There is also a biological difference — horses have not been selectively bred to be less reactive to being herded and transported, unlike cattle and pigs. I have visited livestock slaughtering facilities across the United States as well as in India and Africa and documented my concerns several years ago.

For an in-depth and in-field account of the continuing horrors in the meat industry, which would mean an intensification of this holocaust of the animals if horse slaughter were to become legal in the U.S., read the book by my friend and former co-worker Gail A. Eisnitz, "Slaughterhouse: The Shocking Story of Greed, Neglect and Inhumane Treatment Inside the U.S. Meat Industry."

DEAR DR. FOX: My 2-year-old cat, Purrlie, who, along with her brother was orphaned at five days old and raised by a foster mom, decides every once in a while to stand up in the cat box and pee over the edge in a spraying position.

Lately, she has been doing this more often, and I'm worried about the area around the box becoming permanently "perfumed." I can't figure out what might be triggering this behavior. How clean I keep the box seems to have no impact. There doesn't seem to be an obvious motivating factor. She does not regularly go out, but was outside a little in good weather last summer. I never saw her spray on those outings. — M.T., Lexington Park, Md.

DEAR M.T.: Spraying, a deliberate territorial marking behavior, is unusual in neutered cats. They do, however, quite often start to spray as a territorial marker when upset by the presence of a prowling cat around the house or having met or scented one while outdoors. But she may actually be having difficulty in urinating or be in pain, indicative of bladder inflammation or cystitis and possibly urinary calculi. Corn in the diet can be a contributing factor. A veterinary checkup may be useful to rule out a physical or medical cause. Older cats sometimes miss the box because they are in pain from arthritis and cannot assume the normal posture to evacuate.

In the interim, get a second, larger tray with high sides to help contain her sprayed urine. Feliway is an effective cat pheromone product (available in spray or plug-in dispenser) that may have a calming effect on your cat's psyche when used in the area you have the litter box. A couple of drops of essential oil of lavender on the edge of the box may also help.

Send all mail to or to Dr. Michael Fox in care of Universal Uclick, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns. Visit Dr. Fox's website at

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