Market Emerges for Use of Human Drugs on Pets

Pfizer's Anipryl is designed to treat dogs with Cognitive Dysfunction Syndrome. A new market is emerging for the use of human psychoactive drugs on pets with behavioral problems. The first two such medications to gain U.S. Food and Drug Administration (FDA) approval, both of them for dogs, became available early this year. Novartis Animal Health of Greensboro, N.C., now markets clomipramine hydrochloride, a tricyclic antidepressant used for obsessive-compulsive disorder in humans, under the brand name Clomicalm to treat canine separation anxiety. This condition is precipitated by absence of the pet's owner or attachment figure. Pfizer Animal Health of Exton, Pa., markets selegiline hydrochloride, also known as L-deprenyl, under the brand name Anipryl to treat the Alzheimer's disease-like canine Cognitive Dysfunction Syndrome (CDS). In humans, selegiline primarily treats symptoms of Parkinson's disease, particularly painful foot-cramping. These two behavioral problems in dogs are among a number of pet-owner complaints that are receiving increased attention from veterinarians. Market research by pharmaceutical companies indicates significant sales potential. "We know from our own surveys that about 14 percent of the U.S. dog population exhibits one or more signs of separation anxiety. With 52 million dogs in the U.S., that's [a market of] about seven million dogs," notes veterinarian G.C. Ritchie, product manager for Novartis Animal Health. "I think there's a high level of interest within the profession. When you go to symposia, the rooms where you talk about behavioral problems are overflowing." The signs of canine separation anxiety evaluated in two Novartis multisite trials involving a total of 270 dogs included distress vocalization, destructive behavior, hypersalivation, and inappropriate elimination, all occurring in the owner's absence. Early in these eight-week and 12-week trials, statistically significant differences were observed in improvement or disappearance of signs among dogs that received the drug in combination with behavior modification training, compared to placebo groups that received only behavior modification. The drug is generally well tolerated, although side effects of vomiting, lethargy, and diarrhea were observed in some animals. An abstract has been published and a paper is being prepared.1 Ritchie says Novartis relies on information from surveys and from focus groups of selected veterinarians to help them determine what new products might be needed. Quantitative research is then conducted to establish a viable market, followed by literature searches to determine if a drug intended for humans has been successfully prescribed by veterinarians for off-label use on companion animals. The Animal Drug Use Clarification Act of 1996 allows vets to make such off-label decisions, subject to guidelines similar to those for physicians. Ritchie adds that Pfizer currently is investigating drugs to treat not only behavioral problems in pets, but also cardiological and dermatological conditions. The company's research shows that the biggest pet pharmaceutical market segments are for heartworm prevention, flea control, and routine vaccinations, followed by skin allergies and arthritis. Regarding drugs for behavioral problems, he says, "We're definitely in the growth phase." Photo: Pfizer Animal Health Casey, a 5-year-old retriever mix, and Peter Eeg Dogs diagnosed with cognitive dysfunction suffer an age-related mental decline, not wholly attributable to an unrelated medical condition such as organ failure or infection, that causes them to become disoriented, decrease or alter their responsiveness to family members, change their sleep-wake cycles or activity levels, and/or lose their housetraining.2 A sample of 255 pet owners in Pfizer's unpublished market research indicates that almost half of dogs aged eight or older may exhibit at least one sign of CDS, extrapolating to about 6.5 million dogs nationally. Two unpublished clinical studies by Pfizer, one blinded and the other open label, showed that 69 percent and 75 percent, respectively, of dogs improved in at least one sign of CDS after a month of Anipryl therapy. Some dogs continued to improve for up to three months. Monitoring of adverse reactions in 404 dogs treated for up to 18 months showed that only 4 percent suffered from such side effects as vomiting, diarrhea, or restlessness severe enough to require discontinuation or reduction of dosage. "We know the drugs work at the neurotransmitter level," comments veterinarian Barbara S. Simpson, a specialist in animal behavior, "but whether that is causing the behavioral changes, we don't know." An adjunct assistant professor at the North Carolina State University College of Veterinary Medicine, Simpson also works with individual clients at the privately owned Veterinary Behavior Clinic in Southern Pines, N.C. She is one of only about 20 veterinarians nationwide who are board certified by the American College of Veterinary Behaviorists, a fledgling group recognized by the American Veterinary Medical Association. "Behavior, in human medicine and certainly in veterinary medicine, remains something of a black box. We don't really know what's going on," she admits. "Also, the role of the veterinarian in addressing behavior problems is rather new. That may sound strange, but it's true." She describes aggression, the most common behavior problem among dogs, as, "a can of worms, really. Pharmaceutical companies realize it's a tremendous market, but there are a lot of liability problems." She thinks phobias, anxieties, and compulsive or stereotypic disorders in companion animals are more likely targets of pharmaceuticals to follow the first two behavior drugs. At their worst, such conditions can prompt dogs to crash through windows or engage in other acts that cause extreme destruction of the home and damage to themselves. "Thunder phobia is definitely a problem to treat." She prescribes various human antidepressants and anxiolytics for the problem, combined with desensitization work with the animal, modifications to its environment, and distraction protocols for the owner to follow. Fear of things overhead, such as fans or airplanes, and fear of new experiences or strangers are among other phobias pets suffer. Among the compulsive animal disorders are spinning behavior, tail chasing, excessive licking, or biting at imaginary fleas. Photo: Novartis Animal Health Vocalizations (barking, howling, or whining) are the most common signs of separation anxiety in dogs. Novartis' Clomicalm (left) is designed to treat this disorder. Before the FDA begins the approval of a human medication for pet use, the pharmaceutical company must develop an appropriate dosage for the animal, says Ann Stohlman, a veterinary medical officer in the FDA's Center for Veterinary Medicine. "Cats and dogs and [humans] are all quite different in the way they metabolize drugs." The background data on such a chemical entity's safety is often useful, but even preclinical trials of a drug for human consumption that involved dog models might not be pertinent to the new end use of the drug for the animal. "Not all dog models translate to dog illness," she notes. The three-phase configuration of human trials is not emulated in animal trials, in part because of the expense and the difficulty of recruiting large numbers of companion animals with specific health problems. But essentially, the same FDA approval standards apply for pet drugs as for human drugs, she avers. Nicholas H. Dodman, a professor in the anesthesia and animal behavior department at Tufts University School of Veterinary Medicine, holds five patents on human drugs to manage behavioral problems in pets, and has filed a sixth. An author of popular and scholarly books and articles on animal behavior, he foresees possible treatments not only for dogs and cats, but also birds and horses. Several of his patents cover serotonin-specific reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) to treat aggression in animals. "It seems like, across the animal kingdom from mice to men, drugs of the serotonin variety will decrease aggression," he says. Prozac often is prescribed off label by veterinarians to treat a range of animal behavior problems. Dodman's patents on fluoxetine and other SSRIs arose from a Tufts study of nine dogs that showed a significant reduction in owner-directed dominance aggression after three weeks of treatment.3 He is talking with several smaller pharmaceutical companies about partnerships to develop SSRIs for pet use. "This is a very active area of research." For More Information Association of American Veterinary Medical Colleges 1101 Vermont Ave. N.W., Suite 710 Washington, D.C. 20005 (202) 371-9195 Fax: (202) 842-0773 Web: aavmc.org He also has a "narrow patent" for the anxiolytic buspirone (Buspar), to treat inappropriate elimination in cats, especially failure to use the litter box for urination. He says his early investigations indicate the drug works in about 60 percent of cases, and half remain cured after a short course of treatment. "With this new attitude toward animals as family members rather than utilitarian chattels, people will spend more money on them," Dodman observes, pointing to use nowadays in veterinary medicine of such technologies as CAT scans, radiation therapy, and hip replacement as indications of the growth in demand. "And now that there is a recognition of the magnitude of the behavioral problem, veterinarians are going to want solutions." Steve Bunk is a contributing editor for The Scientist. B.S. Simpson, "Treatment of separation-related anxiety in dogs with clomipramine: results from a multicenter, blinded, placebo controlled clinical trial," Proceedings of the First International Conference on Veterinary Behavioral Medicine, Birmingham, UK, pages 143-54, 1997. W.W. Ruehl and B.L. Hart, "Canine cognitive dysfunction," in N.H. Dodman and L. Shuster, eds., Psychopharmacology of Animal Behavior Disorders, Malden, Mass., Blackwell Science, pages 283-304, 1998. N.H. Dodman et al., "Use of fluoxetine to treat dominance aggression in dogs," Journal of the American Veterinary Medical Association, 209:1585-7, 1996.

Market Emerges for Use of Human Drugs on Pets

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