Naproxen can irritate the stomach and affect platelets, and apixaban thins the blood. Together they greatly raise the risk of serious bleeding, especially from the stomach or bowel.
These medicines can affect each other in a serious way. Do not start taking them together unless your doctor has said it is OK. If you already take both, do not stop either one on your own: speak to your doctor or pharmacist soon.
What to do: Avoid long-term use; monitor for bleeding and consider a PPI.