NSAIDs Metabolism

CYP2C9 handles most of the clearance of NSAIDs (ibuprofen, naproxen, celecoxib, diclofenac). CYP2C8 contributes to certain NSAIDs. Both enzymes show meaningful variant-driven activity differences, which shapes how long the drugs stay active and how much GI, kidney, and cardiovascular stress they place per dose.

Carriers of CYP2C9 reduced-activity variants (CYP2C9*2, *3) are associated with significantly slower NSAID clearance, and elevated risk of GI bleeding, kidney effects, and cardiovascular events at standard doses. Carriers of typical-function variants tend to clear NSAIDs at expected rates and tolerate the standard dose range with fewer adverse events.

Proton pump inhibitors reduce NSAID-induced gastric injury but don't change underlying clearance. Adequate hydration reduces kidney stress. Co-administration with anticoagulants compounds bleeding risk dramatically in slow metabolizers. Topical NSAIDs (gels, patches) deliver therapeutic effect with much lower systemic exposure.

The "I had a bad reaction to ibuprofen" or "GI bleed on a low dose" pattern often hides a CYP2C9 slow-metabolizer genotype. Which variant you carry decides whether standard-dose oral NSAIDs are reasonable maintenance or whether topical, lower-dose, or alternative-class options make better sense.