How Aspirin Thins Blood
Aspirin inhibits cyclooxygenase-1 (COX-1) enzymes in platelets, reducing thromboxane A2 production. This impairs platelet aggregation, prolonging bleeding time and thinning blood.[1]
Why This Harms the Stomach Lining
The same COX-1 inhibition blocks prostaglandin synthesis in the stomach mucosa. Prostaglandins normally protect the lining by promoting mucus and bicarbonate secretion, maintaining blood flow, and buffering acid. Without them, the lining weakens, increasing vulnerability to gastric acid erosion.[1][2]
Resulting Stomach Damage
This leads to direct topical irritation from aspirin's acidity, plus reduced defenses, causing gastritis, erosions, or ulcers. Risk rises with higher doses (>325 mg/day), long-term use, or factors like age, alcohol, or NSAIDs.2
Common Symptoms and Complications
Patients often report dyspepsia, heartburn, nausea, or bleeding (e.g., melena). Severe cases involve perforation or hemorrhage, with annual GI bleed risk at 1-2% for low-dose users, higher (2-4%) for full-dose.3
Who Faces Higher Risks
Elderly, those with H. pylori infection, prior ulcers, or concurrent anticoagulants/steroids see amplified damage. Low-dose enteric-coated aspirin mitigates some topical effects but not systemic COX-1 loss.[2]
Prevention Strategies
Proton pump inhibitors (e.g., omeprazole) restore mucosal protection by cutting acid. Misoprostol replaces prostaglandins. Guidelines recommend PPI co-therapy for at-risk low-dose users.3
[1]: https://www.ncbi.nlm.nih.gov/books/NBK549795/
[2]: https://www.nejm.org/doi/full/10.1056/NEJMra050542