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How soon after ingestion of the pill was it that you sought treatment?
If you knew right away that he'd eaten it, was vomiting induced?
Was he given activated charcoal?
The fact that you were right on top of things increases the chances of a full recovery dramatically.
If vomiting was induced within the first hour after ingestion, and activated charcoal was given to help prevent further absorption of the medication, chances are good that not too much actually got into his bloodstream. The fact that an intact pill was not found is not necessarily worrisome, as if he chewed it we'd expect it to be harder to find, and the stomach acids may also have "melted" it to some extent.
The IV fluids will help flush out his kidneys, in the event that he has absorbed some of the medication. He should also be on gastroprotectants such as sucralfate and famotidine (Pepcid), or misoprostol to guard against gastrointestinal ulceration and bleeding.
The toxic dose for ibuprofen (leading to kidney failure) is about 150 mg/lb; of course, different dogs can be more sensitive. But at this dose, your dog would have needed to ingest 2 pills to be in more serious danger.
You've done everything right and it sounds like he is in very good hands. I think the chances for a full recovery are very good. He will likely be hospitalized for a day or 2 on fluids, and on gastroprotectants for a week or so. Your vet will want to check kidney values again in a day or so, and probably in a week or so, just to be safe.
I wish you and your little guy the best.