Is Naproxen (medication) approved for flight?
There's no fully authoritative source for this information, other than consulting an AME directly. AOPA's medication database is considered pretty reliable (and it says Naproxen is allowed) but their generic disclaimer explains why you can't just look up a medication in a list:


  Although these medications are generally allowed by the FAA for flight
  duties, there are variables with each individual's situation that
  could render a particular medication inappropriate for flying because
  of case history or adverse side effects. Some medications are being
  used "off label". This means that a drug is prescribed for symptoms
  that do not fall within the FDA's approval guidelines for that drug.
  This is just one example of why the FAA might not approve a drug that
  is on the list.


In other words, as with all medical questions you have to consult a  professional to get the right answer for your personal situation.