They've recently approved (in the US) the drug Librela for use in dogs and I've seen adds on tv touting it's use for osteo arthritis pain in older dogs. It's a monthly monoclonal antibody injection that, according to the manufacturer Zoetis, has "minimal involvement" of the liver and kidneys unlike NSAIDs. If your vet has recommended it for your dog, I would recommend doing your own research to see if you want to subject your dog to it. There are many that say it's a miracle drug and helped their pet tremendously however, as I have looked further into it, there are many that have experienced the opposite.
My vet recommended it for my 10yo WPG as she's getting kind of gimpy, partially due to a severely broken leg when she was young. She also has Cushings disease that is well controlled with medication. She got her first shot in January and there weren't any noticeable side effects but also no real improvement in her gait and, in hindsight, maybe a bit worse. In February, when she went back for her second shot, the vet said it might take a couple doses to see a difference. After a few days I could see she was not her normal self, had stopped drinking or eating and more difficulty walking. A trip to the vet for x-rays and blood test revealed very high creatinine and BUN levels indicating severe kidney problems. Her previous test in September were normal. A prescription "kidney diet" was recommended and she was given subcutaneous fluids to ward off dehydration. She has since started drinking and eating a bit with lots of prompting and mostly sleeps. Reading other peoples experiences (there are several online groups) is that it takes a couple months for it to clear their system and some bounce back, if they survive. Is it the Librela? Not according to the people pushing it, but my experience mirrors what many others have experienced. My vet seems to think it is and admitted they were not given much information on adverse reactions. Anyway, just putting it out here if your vet is suggesting it for your pup and to look carefully at what others have experienced.

As an update, my girl Belle took a turn for the worse and went into kidney failure. After 3 days in the vet hospital trying to reverse it, I had to end her suffering today. If your vet is suggesting Librela, look into it carefully. I'm heartbroken that I subjected my best friend to something that may have contributed to her death.

Hang tough. You did the best you could for your girl.
Remember the good times.

tmitch,
Very sorry regarding your dog. As WTM45 said above, you did the best you knew how for her.

I have a Lab who is 13 years old and has some arthritis. She had three shots total. Big improvement after shot 1, not much if any for the remaining two and so I have discontinued. A buddy has a 14 year old Lab from the same line. Has given her two shots so far with very notable improvement in the dogs mobility. Those are the only two samples that I know of personally.

Sorry to hear of her passing.

Try not to dwell on what ifs when, in hindsight, you think a different decision may have been better than the one you made. As others have said, you made the best decision for your dog based on the available information. We always want more time with them, and however long it is, it's never enough.

Thanks, I appreciate the condolences. As dog owners we all will go through the pain/grief/guilt of losing one of our beloved companions. It's much easier to accept when it's a result of an explained occurrence.... old age, disease, etc..... rather than something we might have subjected them to. Coincidence? Guess I'll never really know but I have my doubts, and maybe that's what pains me most.

One can have an overactive immune response to monoclonal antibodies. Also there is the possibility of mild and severe allergic reactions, which are often related to the infusion rate. An infusion should be administered with attention to such things as heart rate, blood pressure, respiration, Another side effect is the possibility of an increased inflammation response which can cause organ damage.

The administration should monitored closely to try and notice any underlying problems.