Aspirin and new COX-2 inhibitors are both used for pain relief and to reduce inflammation, but they have different effects on the stomach lining.

Aspirin, also known as acetylsalicylic acid, is an non-steroidal anti-inflammatory drug (NSAID) that has been in use for over a century. It works by inhibiting both COX-1 and COX-2 enzymes, which are involved in the production of prostaglandins, chemicals that cause inflammation and pain. However, aspirin's inhibition of COX-1 also interferes with the production of prostaglandins that protect the stomach lining, making it more susceptible to damage and increasing the risk of stomach ulcers and bleeding [1].

On the other hand, new COX-2 inhibitors, such as celecoxib and rofecoxib, were developed to reduce the gastrointestinal side effects associated with traditional NSAIDs. They selectively inhibit the COX-2 enzyme, which is primarily involved in inflammation and pain, without affecting the COX-1 enzyme that protects the stomach lining [2]. As a result, COX-2 inhibitors have a lower risk of stomach ulcers and bleeding compared to aspirin [3].

However, it is important to note that COX-2 inhibitors have been associated with an increased risk of cardiovascular events, such as heart attack and stroke, due to their selective inhibition of COX-2 [3]. Therefore, the use of COX-2 inhibitors should be carefully considered and balanced against their potential risks and benefits.

In summary, aspirin and new COX-2 inhibitors have different effects on the stomach lining. Aspirin increases the risk of stomach ulcers and bleeding due to its inhibition of COX-1, while COX-2 inhibitors have a lower risk of gastrointestinal side effects due to their selective inhibition of COX-2. However, COX-2 inhibitors have been associated with an increased risk of cardiovascular events.

Sources:
[1] <https://www.drugpatentwatch.com/p/tradename/ASPIRIN>
[2] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10156439/>
[3] <https://arthritis-research.biomedcentral.com/articles/10.1186/ar1794>