Bone marrow suppression (decreased blood cell counts, particulary neutrophils) and GI toxicity (anorexia, vomiting, diarrhea) are more likely to occur at normal doses in dogs with the MDR1 mutation. Based on some published and ongoing research, it appears that dogs with the MDR1 mutation are more sensitive to these drugs with regard to their likelihood of having an adverse drug reaction. * Vincristine, Vinblastine, Doxorubicin (chemotherapy agents). Higher doses (generally 10-20 times higher than the heartworm prevention dose) have been documented to cause neurological toxicity in dogs with the MDR1 mutation. Similar to ivermectin, these drugs are safe in dogs with the mutation if used for heartworm prevention at the manufacturer's recommended dose. * Selamectin, milbemycin, and moxidectin (antaparasitic agents). This drug should be avoided in all dogs with the MDR1 mutation. At doses used to treat diarrhea, this drug will cause neurological toxicity in dogs with the MDR1 mutation. * Loperamide (ImodiumTM antidiarrheal agent). While the dose of ivermectin used to prevent heartworm infection is SAFE in dogs with the mutation (6 micrograms per kilogram), higher doses, such as those used for treating mange (300-600 micrograms per kilogram) will cause neurological toxicity in dogs that are homozygous for the MDR1 mutation (mutant/mutant) and can cause toxicity in dogs that are heterozygous for the mutation (mutant/normal). There were no other potential causes of neurological toxicity identified in the dog. After withdrawal of the drug, the dogs neurological signs resolved.

A mutant/mutant collie exhibited signs of neurological toxicity after receiving erythromycin. Erythromycin may cause neurological signs in dogs with the MDR1 mutation.

Similar to acepromazine, butorphanol tends to cause more profound and prolonged sedation in dogs with the MDR1 mutation.We recommend reducing the dose by 25% in dogs heterozygous for the MDR1 mutation (mutant/normal) and by 30-50% in dogs homozygous for the MDR1 mutation (mutant/mutant). * Butorphanol (analgesic and pre-anesthetic agent). We recommend reducing the dose by 25% in dogs heterozygous for the MDR1 mutation (mutant/normal) and by 30-50% in dogs homozygous for the MDR1 mutation (mutant/mutant). In dogs with the MDR1 mutation, acepromazine tends to cause more profound and prolonged sedation. The drugs your dog shouldn't be given if they have the MRD1 gene are: Acepromazine (tranquilizer and pre-anesthetic agent). Certain drugs should not be given to Aussies (and a few other dogs) with this MRD1 gene. Now I know you can't believe everything you read online but I am still freaking out a bit.įYI The MRD1 gene has nothing to do with the poison in flea and tick products and epilepsy. I have also been reading a lot online to try and see what could be causing this and some of the possibilities are terrifying. I am currently applying to schools to become a physician assistant and have learned a good bit about medicine and the eyes and while dogs are different than humans we have a lot of similarities in our organs and bodily systems. We have a vet appointment the afternoon and I am a little worried. Today when she woke up her pupil in her all blue eye was the size of a needle and her pupil in her marble eye was huge (this is the same way her eyes were the last time, all blue constricted, marbled dilated) but she hadn't suffered any head trauma, she literally just woke up.ĭid you ever find out what was going on with your puppy? The first time it happened was a week ago, but she had run into a deck (she was playing with another dog and didn't stop quit in time) I noticed the change in her pupil size about 2 hours after the head trauma occurred and it took about 2 hours for it to go back to normal.

She is a blue merles with one blue and one marbled eye. Our aussie pup is 4 months old today and we are having the same issue.

Sightly unequal pupil size in cats