Mdr1 genetic mutation in dogs primary website:
http://www.vetmed.wsu.edu/depts-VCPL/index.aspx
(Note that their information is ongoing and not complete. Also note that this mutation has been found in white GSDs, as well as a black and tan.)

More veterinary information:
http://www.busteralert.org/
http://www.vgl.ucdavis.edu/cghg/mdr1.php

Technical Overview p-glycoprotein transport:
http://www.genemedrx.com/PGP_Introduction.php

List of p-glycoprotein substrates for humans (it is wise to consider dogs at risk to substrates for humans, unless they have been specifically studied and declared okay for dogs): http://www.genemedrx.com/PGPtable.php

I had the MDR1 gene tested at WSU for my dog. WSU was quick to ship the kit, taking the sample was easy, and I got results in 2 weeks. Well worth the money IMO.

Shelley

I agree...I just had Nikki tested last month

I just baffles me each time a see a Heartgard package for medium sized dogs with the picture of a border collie on it.

Sarah, I bet they do that on purpose, since they say low doses *should* be tolerable, and they wanted some of those BC breeds back as customers.

Mdr1 dogs are also susceptible to Revolution, Inerceptor, Sentinel, and ProHeart6. I think that;s not well known. I would say the safest drug for an mdr1 dog is Interceptor at the SafeHeart dose.

I give Sammy Heartguard but not before I confirmed that it was okay with Dr. Mealey at WSU. Haven't had any problems at all because the dosage is so small (and he tested mutant/mutant so would be pretty susceptible to a reaction).

I was nervous, but she assured me that they had no concern whatsoever with the monthly HW preventatives. I don't know that it would matter (because if they were going to react, I think it would be with the first dose they took), but we only give HW preventative six months out of the year here in Colorado - May through October.

As requested :
MDR1 and Relatively adrenal insufficiency

I thought some of you that have Mutant/Mutant dogs might find this helpful.

I received an email via my vet from WSU stating that dogs with the MDR1 mutation can have relative adrenal insufficiency (lower basal cortisols and lower basal ACTH concentrations than dogs that do not have the MDR1 mutation) They haven't tested Mutant/Normal dogs, but they could suffer from the same issue as Mutant/Mutant dogs.
http://onlinelibrary.wiley.com/doi/10.1111/j.1476-4431.2006.00196.x/abstract

The WSU vet indicated that doing a ACTH stim test might be useful.

The WSU vet also said "Research mice that have had the MDR1 gene genetically “knocked out” have a higher incidence of inflammatory bowel disease than “normal” mice."

New canine NSAID which is a human cell line p-glycoprotein substrate: Galliprant

http://www.aratana.com/Galliprant

At this point, until tested by the canine mdr1 folks and given the okay, I would treat it as a canine mdr1 drug. Dogs considering it's use should be tested for the mdr1 mutation.