Aspirin is a widely used medication for pain relief, fever reduction, and anti-inflammatory purposes. However, it can also cause some side effects, including stomach bleeding. Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that works by inhibiting the production of prostaglandins, which are responsible for inflammation, pain, and fever. Prostaglandins also play a protective role in the stomach lining by stimulating the production of mucus and bicarbonate, which neutralizes stomach acid [2].

When aspirin inhibits the production of prostaglandins, it also reduces the protective layer in the stomach, making it more vulnerable to the harmful effects of stomach acid. The reduction of mucus and bicarbonate production can cause the stomach lining to become irritated and inflamed, leading to stomach ulcers and bleeding [2].

The risk of stomach bleeding from aspirin use increases with higher doses, prolonged use, and in individuals with a history of stomach ulcers or bleeding disorders [1]. Other factors that can increase the risk of stomach bleeding include alcohol consumption, smoking, and the use of other NSAIDs or blood-thinning medications [3].

It is important to note that aspirin can also have many benefits, such as reducing the risk of heart attack and stroke in individuals with certain medical conditions. However, it is essential to weigh the potential benefits against the risks and to use aspirin only as directed by a healthcare professional [2].

In conclusion, aspirin can cause stomach bleeding by inhibiting the production of prostaglandins, which reduces the protective layer in the stomach lining. The risk of stomach bleeding increases with higher doses, prolonged use, and in individuals with certain medical conditions or taking other medications. It is crucial to use aspirin as directed by a healthcare professional and to be aware of the potential side effects.

Sources:
[1] Drug Patent Watch. (2021). Aspirin. Retrieved from https://www.drugpatentwatch.com/p/tradename/ASPIRIN
[2] Harvard Health Publishing. (2019). Answers about aspirin. Retrieved from https://www.health.harvard.edu/heart-health/answers-about-aspirin
[3] Sostres, C., Gargallo, C. J., & Lanas, A. (2010). Nonsteroidal anti-inflammatory drugs and upper and lower gastrointestinal mucosal damage. Arthritis research & therapy, 12(Suppl 1), S3. doi:10.1186/ar2883. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086018/