I hate to see animals suffer in movies because you know that an animal who's suffering doesn't understand what's happening, and somehow that just seems to make it worse.
The scene from last night didn't bother me too much, though, because it happened quickly and the dog didn't seem to feel much pain, if any. Odd coincidence, though, that the dog should die just as his master did, so long after taking the pills. As for the patient, I'm inclined to think he must have known about the pills and didn't tell anyone because he wanted to die. I mean, the doctor left the pills with him and told him to take them, and all of a sudden they'd disappear and he wouldn't think anything of it?