Published results can be found here.

Study Start Date: 01/01/2005
Study End Date: 11/01/2006

MDR-1 genotype in dogs treated with milbemycin for generalized demodicosis

It is known that mutations in the mdr-1 gene can predispose dogs to have adverse neurologic effects when administered a drug that is a P-glycoprotein substrate. Ivermectin is such a drug and has been shown to cause adverse reactions in both mdr-1 homozygous mutants and heterozygotes. Affected dogs may experience similar toxicity with other avermectins, such as milbemycin oxime. There are conflicting data regarding milbemycin oxime, with some studies demonstrating no adverse affects in rough-coated collies treated with daily milbemycin oxime, whereas others have documented toxicity with this drug. There have not been any studies documenting the mdr-1 genotype of dogs treated with milbemycin for generalized demodicosis. We are obtaining cheek swab DNA samples from dogs that were treated with milbemycin for generalized demodicosis to determine their MDR-1 genotype. We will compare the genotype with the breed, dose of milbemycin, severity of clinical signs, and reaction to other avermectins.

We hope to provide recommendations about the use of milbemycin for demodicosis in dogs with mdr-1 mutations based on mdr-1 genotyping results and clinical outcomes.

Inclusion criteria:

1. Herding breed treated with milbemycin for generalized demodicosis (with or without adverse effects).
2. Any breed treated with milbemycin for demodicosis WITH adverse effects.
3. Any breed treated with milbemycin WITHOUT adverse effects but WITH adverse effects to ivermectin.

Exclusion Criteria:
Any breed, other than herding, treated with milbemycin with NO problems (unless had problem with ivermectin).

Samples:
Two cheek swabs samples will be submitted per patient. The swabs will be mailed out to either the veterinarian or the client, along with an instruction sheet.

Costs/Reimbursements:
The investigators will pay for shipping swabs to clinicians, and return shipping, as well as all genotyping.
Veterinarians will be informed of the mdr1 status of their clients' pets.

Full Disclosure information:

• The study is funded by intramural institutional funding (UCDavis VMTH). The investigators do not have any conflict of interest.
• Participants need to provide informed consent from their clients
• The study will be published if results are negative
• The study will be reported on VIN
• The authors will recognize, acknowledge or include VIN as a co-author if the study is published