"The exercise-induced changes in PGF(2alpha) and PGE(2) were not different between the ibuprofen and acetaminophen groups. These results suggest that ibuprofen and acetaminophen have a comparable effect on suppressing the normal increase in PGF(2alpha) in human skeletal muscle after eccentric resistance exercise, which may profoundly influence the anabolic response of muscle to this form of exercise."
It doesn't seem to affect total body protein metabolism, but definitely affects skeletal muscle...and it looks to be a great way to shoot yourself in the foot.
No pain, no gain, eh?