A few years ago, on the basis of my symptom tracking, I convinced my GP that ibuprofen was making a difference and she agreed to prescribe Mobic (meloxicam) as a trial (or perhaps she humoured me). It didn't work. My understanding is that Mobic is a COX-2 inhibitor whereas ibuprofen is both a COX-1 and COX-2 inhibitor. Whether the different COX inhibition accounts for ibuprofen reducing the likelihood of PEM and other symptoms for me while Mobic does not, I don't know. (At one point I understood what COX-x inhibition meant but I have long forgotten it.) I haven't tried naproxen. It looks as if naproxen is both a COX-1 and COX-2 inhibitor. So perhaps I would also find naproxen useful. @leokitten, why do you ask?