PTGS2 and myocardial infarction: The COX-2 selective NSAID rofecoxib at low doses (50 mg daily) increased the occurrences of myocardial infarction by 0.5% in approximately 8000 patients with rheumatoid arthritis compared to 0.1% in those treated with naproxen (500 mg twice daily), indicating a severe thrombogenic effect of rofecoxib compared to naproxen [47].