When was he neutered? He shouldn't need to be on it for very long, it sounds like he's been getting it for days?
Rimadyl seems kind of unnecessary, I don't believe it's usually used for such a simple procedure. I mean, it's not even normally given out for spays which are more invasive. And to prescribe it for a week?He was neutered on July 18. They had us give it to him once in the morning and once at night, he took his last one Tuesday, which was July 26, so he was on it for 7 days (he started it on July 19).