Aspirin and Rofecoxib are both medications used to treat pain and inflammation, but they have different effects on the stomach lining.

Aspirin, also known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug (NSAID) that can irritate the stomach lining, causing stomach ulcers and other gastrointestinal (GI) side effects [1]. This is because aspirin inhibits both cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzymes, which are involved in the production of prostaglandins that protect the stomach lining [2].

On the other hand, Rofecoxib is a selective COX-2 inhibitor, which means it specifically inhibits the COX-2 enzyme and has less effect on the COX-1 enzyme [3]. This makes Rofecoxib less likely to cause stomach ulcers and other GI side effects compared to aspirin [4]. However, Rofecoxib has been associated with an increased risk of cardiovascular events, such as heart attack and stroke, which led to its withdrawal from the market in 2004 [5].

In summary, aspirin and Rofecoxib have different effects on the stomach lining due to their different mechanisms of action. Aspirin inhibits both COX-1 and COX-2 enzymes, which can cause stomach irritation and ulcers, while Rofecoxib selectively inhibits the COX-2 enzyme, making it less likely to cause stomach side effects.

Sources:

1. "Aspirin." National Library of Medicine, drugs.nlm.nih.gov/druginfo/aspirin.html.
2. "How Aspirin Works." Arthritis Foundation, www.arthritis.org/health-wellness/treatment/medication/aspirin-and-other-salicylates/how-aspirin-works.
3. "Rofecoxib." National Library of Medicine, drugs.nlm.nih.gov/druginfo/rofecoxib.html.
4. "Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)." Mayo Clinic, www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/nonsteroidal-anti-inflammatory-drugs-nsaids/faq-20058136.
5. "Rofecoxib (Vioxx)." DrugPatentWatch, www.drugpatentwatch.com/rofecoxib.