Likely mistake: You took too many for too long, leading to side effects like rebound headaches or problems with your gastrointestinal system (ibuprofen) or liver (acetaminophen).
Get the most out of your treatment: Ibuprofen and acetaminophen affect people differently, but both have been shown to be effective remedies for ordinary tension headaches. The problem comes when they work too well...and you stop counting pills and start popping handfuls. If you're using these meds for longer than a couple of weeks, limit your dose to 2,500 mg a day (under a physician's supervision) says Lynn R. Webster, MD, medical director and founder of Lifetree Clinical Research & Pain Clinic and president-elect for the American Academy of Pain Medicine.
Keep in mind: Can't decide which one to take? Try both. Webster says alternating your use of ibuprofen and acetaminophen can lower the risks of side effects from taking just one.