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According to my doctor, 4 hours. You can switch them up. Take acetaminophen, (Tylenol), then wait 4 hours and take Ibuprofen, wait another 4 hours and take acetaminophen and so on. :) 15 people found this useful.
If you are taking another NSAID like aspirin or naproxen you should wait at least six hours from your most recent dose of ibuprofen. If whatever pain you're experiencing wasn't adequately controlled by the ibuprofen you took earlier, you could take 500 mg acetaminophen along with 800 mg ibuprofen every eight hours.