Ok I read in internet, that they stop the formation of prostaglandins which are required to make the stomach mucosa. How do prostaglanding affect stomach mucosa? Also since it is an anticoagulent it should make the bleeding worse. Thanks

Aspirin does cause anticoagulation, so it does make the bleeding worse. Specifically thromboxane A₂ formation is inhibited. Thromboxane A₂ is responsible for platelet aggregation which causes blood clotting, so inhibiting it reduces clotting and increases bleeding. It's all in the Wikipedia article

Stomach irritation. Aspirin can irritate the stomach lining and cause heartburn, pain, nausea, vomiting and, eventually, the most serious consequences, such as internal bleeding, ulcers and holes in the stomach or intestines. chronic drinkers may be at increased risk of stomach bleeding and liver damage, use of aspirin.

Edited February 18, 201114 yr by jimfaster