Aspirin is a widely used medication that is commonly used to relieve pain, reduce fever, and prevent blood clots. However, it is important to be aware of the potential side effects of aspirin, including stomach ulcers and bleeding.

According to Drug Patent Watch [1], aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that can irritate the lining of the stomach and cause stomach ulcers. The risk of developing stomach ulcers is higher in people who take aspirin regularly or in high doses. Additionally, aspirin can also increase the risk of bleeding in the stomach and intestines, which can be life-threatening in some cases.

A study published in the US National Library of Medicine [2] found that the use of aspirin can increase the risk of gastrointestinal bleeding, including stomach ulcers, especially in elderly patients. The study also found that the risk of bleeding was higher in patients who took aspirin in combination with other NSAIDs or anticoagulants.

The NHS [3] states that the risk of developing stomach ulcers or bleeding is higher in people who have a history of stomach ulcers, bleeding disorders, or are taking other medications that increase the risk of bleeding. The NHS advises people to talk to their doctor before taking aspirin if they have any of these risk factors.

In conclusion, aspirin can cause stomach ulcers and bleeding, especially in people who take it regularly or in high doses. The risk of developing these side effects is higher in people who have a history of stomach ulcers, bleeding disorders, or are taking other medications that increase the risk of bleeding. It is important to talk to a doctor before taking aspirin if you have any of these risk factors.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ASPIRIN
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970722/
[3] https://www.nhs.uk/medicines/aspirin-for-pain-relief/side-effects-of-aspirin-for-pain-relief/