A 58-year-old man with osteoarthritis is prescribed naproxen (non-selective NSAID) for chronic pain. Which adverse effect profile best distinguishes naproxen from acetaminophen in this patient?

Explanation

## Comparison: NSAIDs (Naproxen) vs Acetaminophen ### Cardiovascular Risk: The Key Discriminator **Key Point:** Non-selective NSAIDs like naproxen inhibit both COX-1 (in platelets) and COX-2 (in vascular endothelium). This dual inhibition creates a **prothrombotic state**: reduced platelet thromboxane A₂ (TXA₂) is offset by loss of endothelial prostacyclin (PGI₂), resulting in **net increased cardiovascular risk** [cite:Harrison 21e Ch 297]. **High-Yield:** Naproxen and other non-selective NSAIDs increase the risk of **myocardial infarction, ischemic stroke, and venous thromboembolism** by 20–50% depending on baseline cardiovascular risk. Acetaminophen has **no significant cardiovascular risk**. ### Comparative Toxicity Profile | Adverse Effect | Naproxen (NSAID) | Acetaminophen | |---|---|---| | **Cardiovascular (MI/stroke)** | ↑↑ Increased | ↔ No increased risk | | **GI ulceration** | ↑↑ Significant | ↔ Minimal | | **Hepatotoxicity** | Rare at therapeutic doses | ↑ At overdose (>4 g/day) | | **Acute kidney injury** | ↑ (via COX-2 inhibition) | ↔ Rare | | **Thrombocytopenia** | Rare | Rare | ### Why NSAIDs Are Prothrombotic ```mermaid flowchart LR A["NSAID (Naproxen)"]:::action --> B["Inhibits COX-1 & COX-2"]:::outcome B --> C["↓ Platelet TXA₂"]:::outcome B --> D["↓ Endothelial PGI₂"]:::outcome C --> E["↓ Platelet aggregation"]:::outcome D --> F["↓ Vasodilation & anticoagulation"]:::outcome E --> G["Net prothrombotic state"]:::urgent F --> G G --> H["↑ MI/Stroke risk"]:::urgent ``` ### Clinical Pearl **Clinical Pearl:** Acetaminophen has minimal COX inhibition and no antiplatelet or anticoagulant effects, making it the safer choice for patients with high cardiovascular risk (prior MI, stroke, diabetes, hypertension). NSAIDs should be avoided or used at the lowest dose for the shortest duration in such patients [cite:KD Tripathi 8e Ch 12]. ### Mnemonic **Mnemonic:** **NSAID Cardiovascular Risk = TXA₂ Loss > PGI₂ Loss** — The loss of platelet TXA₂ is transient (platelets cannot synthesize new COX), but endothelial PGI₂ loss is sustained, tipping the balance toward thrombosis.