A recent groundbreaking study of clinical, histological and immunological data of 22 cases of Pemphigus foliaceus, or PF, shows evidence that it can occur as an adverse drug reaction to the canine flea and tick preventive ProMeris.
PF is the most common spontaneously occurring autoimmune dog skin disease and typically displays as lesions on the face, nasal planum and ears. The reaction is rare but serious, says the study’s lead author, Thierry Olivry, DrVet, Ph.D., Dipl. ACVD, of North Carolina State University.
Ultimately, ProMeris Duo (Metaflumizone–amitraz ), which is also used for treating demodicosis, will be discontinued. The product, marketed by Pfizer Animal Health, will be available while supplies last or until mid-September. ProMeris Duo is called ProMeris for Dogs in the United States.
“ProMeris was one of the many products that Pfizer brought into its portfolio when we acquired Wyeth/Fort Dodge Animal Health,” says Jim Brick, director and team leader of U.S. marketing for Pfizer Inc.
“We have completed a thorough review and evaluation of the strategic fit into the Pfizer Animal Health portfolio, and have made the decision to discontinue the manufacture and sale of Promeris flea and tick control for dogs and cats.
“We notified our current customers of this decision in early April and will continue to fill their orders until Sept. 20, 2011, or while supplies last. We look forward to continuing to meet the needs of our customers with our evolving parasiticide portfolio.”
The study that gathered and presented the ProMeris findings was conducted by Dr. Olivry; Ursula Oberkirchner, resident; and pathologist Keith Linder, D.V.M., Ph.D., all of North Carolina State University.
Since ProMeris’ introduction to U.S. and European markets in 2007, veterinarians have reported this adverse reaction, but previous case studies failed to use a drug-reaction probability scale and therefore an ADR couldn’t be definitively identified.
Olivry says this examination of all parameters studied suggests that this ADR might represent the first instance of contact drug-triggered PF to be published in Veterinary Dermatology. The article was published in the March issue of the journal.
Spontaneously occurring PF, thought to develop through genetic and environmental triggers, has a higher prevalence in Chow Chows and Akitas, whereas ProMeris-triggered PF has a higher occurrence in Labrador Retrievers and other large-breed dogs, Olivry says.
The study found that ProMeris Duo-associated PF not only had a reaction to the same drug, but also shared many of the same phenotypes. Lesions in PD-triggered PF were found to be both localized and at distant locations from the point of application.
“We contacted specialists who had diagnosed these cases in the United States and Europe,” Olivry says. “Dogs were selected if they had a history of skin lesions that first arose at the PD application site, but dogs with a known history of autoimmune disease were omitted.
“Referring veterinarians from cases used completed questionnaires providing information on the patient’s lesions and drug application history. Within the 22 dogs included in this study, two groups of affected animals were distinguished: dogs with localized signs or those who also exhibited distant skin lesions.”
Olivry’s goal in revealing his study findings is to provide veterinarians with information on the prognosis and management of this disease. In addition to skin lesions, more severe reactions can occur and can be long-lasting.
“Signs of systemic illness were reported in three dogs in the study, and four required immunosuppressive treatment,” Olivry says. “After ADR PD lesions occur and are then treated, they could recur at a later time without reapplying ProMeris Duo.”
Before ProMeris became available for veterinary purchase and distribution, studies evaluating its safety and efficacy reported the development of skin lesions at the site of drug application in some treated animals, Olivry says. In one clinical trial enrolling dogs with flea or tick infestation, six of 293 subjects (2 percent) exhibited skin hyperpigmentation, hair matting or scales at application sites.
In another experimental study of dogs infested with either fleas or ticks, one dog treated with ProMeris developed dorsal skin lesions that required treatment with an anti-inflammatory drug for seven days.
“Specific information on the frequency of these severe adverse drug reactions isn’t available, but it is important that veterinarians are aware of the product’s potential to cause the patient harm,” Olivry says. “Caution needs to be exercised if a vet decides to use this drug.”