My 17 mo old BLF has been on Trifexis for the last 6 or 7 months and pretty much has had no problems with it that I noticed. That is, up until a few days ago. I gave her the regularly scheduled monthly dose on Sunday night. Monday afternoon when I got home from work, all was well... she was happy and energetic, everything seemed normal. A short while later I sat down to relax and she went to sleep on the couch. After about an hour I noticed she was still sleeping, which was unusual because it was her supper time. I said the word "hungry" and like always her ears perked up. But I noticed she looked like she was having problems getting up, and she had a glazed look in her eyes. I picked her up and sat her down on the floor and she fell down! Her back end had completely given out on her and she couldn't walk or stand. I immediately searched the house and yard for anything she could have gotten into, but nothing. By this time the vet was closed and they did not answer their emergency number. I thought maybe she'd snap out of it so I just let her sleep it off. Around 11:30 my wife got home from work. After some quick googling, we were afraid maybe she had a bad infection in the uterus or something. So, by midnight or so, we were off to the emergency clinic about an hour away. They checked her out, vital signs were fine, normal heart rhythm, etc. I was baffled when they walked her out of the back room on a leash and she was wagging her tail. Vet said maybe an adverse reaction to the Trifexis, but wasn't sure. They advised us to let her sleep it off and check her out in the morning. By morning, Betty was no better. She still could not get up on her own and could barely stand on her own. When she'd squat to piss she'd fall over. So, that morning my wife took her in to our normal vet for a visit. Again, vital signs were all good. Our vet was certain that it was a bad reaction to the Trifexis, and he actually called the company to make a complaint because this was the second dog that came through his office for the same problems. He sent Betty home with advice to let her rest, but he wasn't 100% sure how she'd recover. Thankfully, by today, she seems to be pretty much back to normal... although she does still seem to be sleeping quite a bit. At least she's running around on her own again!
This was an extremely frightening couple of days for us. Obviously she's a family companion, but as I watched her lay around, half-paralyzed, I couldn't help but think of all the hours of training and all the money that's gone into her. To think, all that could seemingly be taken away by a stupid pill... Just because it's a convenient "all-in-one" type of medication. Scary stuff for sure.
I know this is a rarity, but after researching it online I found many similar stories involving the same medication. I never thought she'd have any side effects since she had done so well on it months prior, but I guess that the past "success" with it was totally irrelevant. Live and learn I guess. I know one thing, I won't be giving my dog this drug ever again, and I certainly won't recommend it to anyone else either. Just doesn't seem worth the risk to me.