A 58-year-old man with Type 2 diabetes and elevated triglycerides (480 mg/dL) is started on a fibrate. Which feature best distinguishes fibrate-induced myopathy from statin-induced myopathy?

Explanation

## Fibrate-Induced vs. Statin-Induced Myopathy ### Fibrate-Induced Myopathy **Key Point:** Fibrate myopathy is **potentiated by concurrent statin use** and is dose-dependent on statin intensity. The combination increases myopathy risk 5–10 fold. - Mechanism: Fibrates inhibit renal clearance of statins (especially pravastatin, rosuvastatin) → increased statin levels → myotoxicity - Risk factors: renal impairment, high-dose statin, older age, diabetes - Presentation: myalgia, weakness, elevated CK (often mild to moderate) - **Distinguishing feature:** Risk is **statin-dependent** — myopathy risk increases with statin dose and fibrate co-administration ### Statin-Induced Myopathy **Key Point:** Statin myopathy can occur **independently**, even without fibrate co-administration. - Mechanism: Reduced mevalonate pathway → decreased CoQ10, ubiquinone, dolichol synthesis → impaired muscle mitochondrial function - Risk factors: high-dose statin, renal/hepatic impairment, older age, female sex, drug interactions - Presentation: myalgia (most common), myositis (rare), rhabdomyolysis (very rare) - **Distinguishing feature:** Can occur as **monotherapy**; not dependent on fibrate co-administration ### Comparative Table | Feature | Fibrate Myopathy | Statin Myopathy | | --- | --- | --- | | **Mechanism** | ↑Statin levels via renal clearance inhibition | ↓CoQ10, impaired mitochondrial function | | **Fibrate co-admin required?** | **YES** (potentiation) | NO (can occur alone) | | **Statin dose-dependent?** | **YES** | YES | | **Reversibility** | YES (both are reversible) | YES (both are reversible) | | **CK elevation** | Mild to moderate | Mild to severe (rhabdo possible) | | **Prevention** | Avoid high-dose statin + fibrate; monitor CK | Use lower statin doses; CoQ10 supplementation (unproven) | **High-Yield:** The **single best discriminator** is that fibrate myopathy is **fibrate-statin interaction–dependent** (myopathy risk rises with statin intensity), whereas statin myopathy can occur as **monotherapy**. **Mnemonic:** **FIBRATE + STATIN = ↑↑ MYOPATHY RISK** — the combination is the red flag. Statin alone can cause myopathy, but fibrate myopathy almost always requires a statin co-dose. **Clinical Pearl:** When combining fibrate + statin, use a **lower-intensity statin** (pravastatin 20–40 mg or rosuvastatin 5–10 mg) and monitor CK at baseline and 6–12 weeks. If myalgia develops, check CK and renal function; if CK is >3× ULN or symptoms are severe, discontinue both drugs. [cite:KD Tripathi 8e Ch 32; Harrison 21e Ch 397]