In doing our own research, it is important to remember that just because it is published on the internet
does not mean it is true! It is dangerous to take anecdotal evidence...somebody's highly subjective experience...as fact. They may be blaming the drug...or vet...or procedure...without regard to the real facts.
That said, I have nothing against research...just make sure you give the strongest weight to the resources that are most credible...like research posted in peer-reviewed journals or research papers by scientific teams...or government websites.
That said, here is something I found about Previcox posted on the FDA website.
Please note it is contraindicated for dogs under 12.5 lbs!! The vet should have known better!
http://www.fda.gov/cvm/Documents/N141230cis.pdf