Robo "Mysql Blazing Hot" Robo was my first Aussie - he was my absolute pride & joy. He barely left my side (except when we'd been at the horses too long and he wanted to play with the other dogs) & we did everything together.
Back then, I had a very basic knowledge of MDR1. I knew it was an ivermectin sensitivity (and that Robo likely had the mutation) but didn't know just how many drugs could pose a problem. So when he got mange (probably from a nearby fox), I only made sure I wasn't giving him Ivermectin. We gave him Revolution (selamectin) & it took care of the mange. Every couple of months I also gave him a preventative dose (as I really didn't want him getting mange again), not realising selamectin is related to ivermectin (seems obvious now). Apparently, selamectin is safe in low doses (i.e. for heartworm) but the dose rate for treating mange is a fair bit higher & tends not to be safe in MDR1 affected dogs. At the time I didn't know this so when he started having seizures, we weren't sure what was the culprit. Sadly his seizures got closer & closer together (started off maybe once a month, at one point they were weekly) until he had a bout of cluster seizures a few days after a dose of Revolution. It was only then that we actually realised it may have been the selamectin causing the issue. On the day of cluster seizures we took him to the vet & he stayed overnight on a drip. He had had over four seizures that horrible day, he was disoriented, appeared to be having vision problems & could barely walk. The next morning he seemed a lot better & was so happy to see us.
We thought that was the end of it & the drug had left his system but he kept having the seizures. The vets had given us Diazepam (Valium) to give him when there was a seizure coming so I'd give him one of them each time (as directed) to try lessen the effects of the seizure. Eventually there was a day where he had almost non-stop cluster seizures, he could barely see & the valium wasn't helping. We had to let him go on the 30th November, 2014 - he was only 18 months old. I don't think I've ever cried so much in my life as he was so special to me.
I have written this out as a cautionary tale - I wish I had done a lot of things differently (let's start by saying I wouldn't have given him Revolution if I knew it would be an issue). I think a large problem is that vets here in Australia are very underinformed about MDR1 in certain breeds & the drug companies don't like to hear of there being an issue with their product. For more information on MDR1 in Australian Shepherds, click here.