Statins and Lipid-Lowering Agents
Statins are the cornerstone of lipid-lowering therapy, reducing cardiovascular events by inhibiting HMG-CoA reductase. Newer agents like PCSK9 inhibitors offer additional LDL reduction.
## Statins: Mechanism of Action
Statins competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis. Reduced intracellular cholesterol upregulates LDL receptors on hepatocytes, increasing clearance of LDL-cholesterol from the blood. This mechanism produces 30-55% LDL reductions depending on the agent and dose.
## Available Statins
| Statin | LDL Reduction | Metabolism | Key Feature |
|--------|--------------|------------|-------------|
| Rosuvastatin | 45-55% | Minimal CYP | Most potent |
| Atorvastatin | 40-50% | CYP3A4 | Long half-life, no food requirement |
| Simvastatin | 30-40% | CYP3A4 | Prodrug, many interactions |
| Pravastatin | 25-35% | Non-CYP | Fewest drug interactions |
| Pitavastatin | 30-40% | Minimal CYP | Lipid-neutral to HDL-raising |
High-intensity therapy (rosuvastatin 20-40 mg, atorvastatin 40-80 mg) is recommended for patients with established atherosclerotic cardiovascular disease (ASCVD) and for primary prevention in high-risk individuals.
## Pleiotropic Effects
Beyond LDL lowering, statins stabilize atherosclerotic plaques, improve endothelial function, reduce vascular inflammation (lower CRP), and have antiplatelet effects. These pleiotropic mechanisms contribute to cardiovascular event reduction beyond what LDL lowering alone would predict.
## Adverse Effects
**Myopathy** -- The most clinically significant concern, ranging from myalgias (muscle pain, 5-10% of patients) to rare rhabdomyolysis. Risk increases with higher doses, drug interactions (CYP3A4 inhibitors with simvastatin), hypothyroidism, and renal impairment. Creatine kinase should be checked if symptoms develop.
**Hepatotoxicity** -- Transaminase elevations >3x upper limit of normal occur in <1% of patients. Routine liver function monitoring is no longer recommended by most guidelines.
**New-onset diabetes** -- Statins slightly increase diabetes risk (9-12% relative increase), primarily in patients already at risk. The cardiovascular benefit outweighs this risk in most populations.
## Non-Statin Lipid-Lowering Agents
- **Ezetimibe** -- Blocks intestinal cholesterol absorption via NPC1L1 transporter. Adds 15-20% LDL reduction when combined with a statin. Well-tolerated.
- **PCSK9 inhibitors** (evolocumab, alirocumab) -- Monoclonal antibodies that prevent LDL receptor degradation, achieving 50-60% additional LDL reduction. Injectable, expensive, reserved for high-risk patients or statin intolerance.
- **Bempedoic acid** -- Inhibits ATP citrate lyase upstream of HMG-CoA reductase. Does not cause myopathy (prodrug activated only in liver). Useful in statin-intolerant patients.
- **Fibrates** (fenofibrate) -- Primarily reduce triglycerides via PPAR-alpha activation. Modest HDL increase.
- **Icosapent ethyl** -- Purified EPA that reduces cardiovascular events in patients with elevated triglycerides on statin therapy (REDUCE-IT trial).
## Key Takeaways
- Statins remain the most effective and evidence-based class for cardiovascular risk reduction.
- High-intensity statin therapy is standard for secondary prevention of ASCVD.
- PCSK9 inhibitors and bempedoic acid provide options for patients who cannot tolerate statins.
- Myopathy risk is real but manageable -- dose adjustment and statin switching resolve most cases.