I know, that pyr pain tolerance is just out of this world. Halley never gave so much as a whimper.
The only way that I could tell that she was in pain was by her breathing, the look in her eyes, and whether or not she'd eat and drink. I've learned to watch for those things, b/c otherwise you usually can't tell with a pyr.
Last week we took Sammy into the vet to have his teeth cleaned and checked (he has dental problems from all of the years of neglect & malnutrition). He'd had his teeth cleaned and a bad molar extracted in February by rescue and we'd had the vet check his teeth in May when he had his last vet visit and all was ok. Meanwhile he's been eating dry food and never once has he tipped his head sideways as he was crunching to avoid a bad tooth (I know, b/c I've been watching). Still at the vet check last week he had another bad tooth that had to be pulled, and it must have been hurting. I felt awful, b/c we'd been watching for more problems, but he didn't show the slightest symptom and it hadn't showed up in May at the vet. Anyway, the tooth was pulled last week and he's loving all of the canned food now. Sam was on Deramaxx for about a week after the tooth was pulled and Halley was on it, also. They both were lethargic, but that could be from the underlying problem (cancer and tooth extraction). I found this web site that gives some info and it does list depression as a possible side effect, so maybe? If it makes Yukon sleepy right now though, that would probably be a good thing since he's supposed to be resting. I'd just make sure that he eats with his meds though. My best friend's dog was on Deramaxx a few weeks ago and she developed some gastric problems. I hope that this helps.
http://www.deramaxx.com/content/info.asp#link_8