Cardiovascular · Medicine Class

Statins (HMG-CoA Reductase Inhibitors)

Competitive inhibition of HMG-CoA reductase

Mechanism of Action

Statins competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis. This reduces intrahepatic cholesterol, which upregulates hepatic LDL receptors, increasing clearance of LDL-cholesterol from the circulation. Beyond LDL lowering, statins have pleiotropic effects: anti-inflammatory, endothelial-stabilizing, and plaque-stabilizing properties that contribute to their cardiovascular benefit independently of cholesterol lowering.

Therapeutic Indications

Primary and secondary prevention of atherosclerotic cardiovascular disease (ASCVD)
Hypercholesterolemia (elevated LDL-C)
Hypertriglyceridemia (adjunctive)
Familial hypercholesterolemia
Post-myocardial infarction (high-intensity statin regardless of baseline LDL)
Stroke prevention in patients with established ASCVD
Diabetic patients ≥40 years (per ACC/AHA guidelines)

Medicines in This Class

Atorvastatin (Lipitor)

High-intensity: 40–80mg/day. Most widely prescribed statin. ~45–55% LDL reduction at max dose.

Rosuvastatin (Crestor)

High-intensity: 20–40mg/day. Most potent per mg. ~55–63% LDL reduction at max dose. Hydrophilic.

Simvastatin (Zocor)

Moderate-intensity (20–40mg). FDA limits 80mg due to myopathy risk. Significant CYP3A4 interactions.

Pravastatin (Pravachol)

Moderate-intensity. Hydrophilic, fewer CYP interactions, preferred with immunosuppressants.

Lovastatin (Mevacor)

Moderate-intensity. First approved statin (1987). CYP3A4 substrate — multiple interactions.

Fluvastatin (Lescol)

Low-to-moderate intensity. CYP2C9 substrate. Fewer interactions than CYP3A4-metabolized statins.

Pitavastatin (Livalo)

Moderate-intensity. Minimal CYP metabolism. Good option in patients on CYP3A4 interacting medicines.

Class-Wide Side Effects

Common Side Effects

Myalgia (muscle pain) — 5–10% of patients
Gastrointestinal symptoms (nausea, constipation, diarrhea)
Elevated liver enzymes (transaminase increases) — usually mild, transient
Headache and sleep disturbances (rare)

Serious Side Effects

Myopathy — significant muscle damage (CK > 10× ULN)
Rhabdomyolysis — severe muscle breakdown with renal failure (rare, ~1 in 10,000)
Immune-mediated necrotizing myopathy (IMNM) — anti-HMGCR antibodies; may persist after statin discontinuation
Statin-induced hepatotoxicity — serious but very rare (<1 in 10,000)
New-onset type 2 diabetes (modest increased risk, 10–12% relative increase)

Class Medicine Interactions

CYP3A4 inhibitors (azole antifungals, macrolides, HIV protease inhibitors) → increase lovastatin/simvastatin/atorvastatin levels → myopathy risk

Gemfibrozil → increased statin levels (inhibits glucuronidation) → myopathy risk — avoid combination

Cyclosporine → significantly increases all statins → myopathy risk; max statin doses apply

Warfarin → some statins increase INR; monitor closely

Amiodarone → inhibits CYP3A4 and CYP2C9; max simvastatin 20mg

Contraindications

!Active liver disease or unexplained persistent transaminase elevations
!Pregnancy and breastfeeding (Category X)
!Concomitant strong CYP3A4 inhibitors (for simvastatin/lovastatin): boceprevir, itraconazole, ketoconazole, certain HIV meds
!History of statin-associated autoimmune myopathy with the same or similar statin

Monitoring Parameters

Lipid panel: baseline, 4–12 weeks after initiation, then annually
Liver function tests: baseline only (routine monitoring not required in absence of symptoms)
CK: baseline; repeat if myalgia develops (>10× ULN indicates myopathy; >40× with symptoms suggests rhabdomyolysis)
Fasting glucose / HbA1c: baseline in at-risk patients
Symptom review: muscle pain, weakness, tenderness at each visit

Frequently Asked Questions

Do all statins work the same way?

All statins share the same mechanism (HMG-CoA reductase inhibition) but differ significantly in potency, pharmacokinetics, medicine interactions, and tissue selectivity. High-intensity statins (atorvastatin ≥40mg, rosuvastatin ≥20mg) reduce LDL by ≥50%. Moderate-intensity statins reduce LDL 30–50%. Hydrophilic statins (rosuvastatin, pravastatin) may have fewer muscle-related side effects and fewer CNS effects than lipophilic statins.

What should I do if I develop muscle pain on a statin?

Mild muscle aches without CK elevation are common and often resolve. Try taking the statin with food, switching the dose time to evening, or switching to a different statin (especially a hydrophilic statin). If muscle pain is severe, or accompanied by dark urine, weakness, or markedly elevated CK, stop the statin immediately and contact your healthcare provider — rhabdomyolysis is a medical emergency.

Do statins cause liver damage?

Serious statin-induced hepatotoxicity is extremely rare. Mild, asymptomatic transaminase elevations (up to 3× ULN) occur in ~1% of patients and are dose-related and reversible with dose reduction or discontinuation. Routine liver function monitoring beyond baseline is no longer recommended by ACC/AHA guidelines in the absence of symptoms.

Can I stop taking my statin if my cholesterol is normal?

Not without consulting your doctor. Statins are often prescribed for cardiovascular risk reduction, not just cholesterol lowering — especially after a heart attack or stroke. Stopping a statin may increase cardiovascular event risk. Your "normal" cholesterol on a statin reflects the medicine's effect, not your natural level. Discuss with your cardiologist before any changes.