Clinical pharmacology
A clinical pharmacology reference for HMG-CoA reductase inhibitors — covering mechanism of action, potency ranking, pharmacokinetic differences between agents (lipophilicity, CYP3A4, OATP1B1), drug interactions, statin-associated muscle disease, PCSK9 inhibitors, and non-cardiovascular safety.
Statins vary substantially in LDL-C reduction at standard doses, CYP metabolism, lipophilicity, and drug interaction profiles. The table below summarises clinically relevant differences.
The mechanism of action of statins centres on competitive inhibition of HMG-CoA reductase — the rate-limiting enzyme in the mevalonate pathway of hepatic cholesterol biosynthesis. By reducing intracellular cholesterol, statins trigger upregulation of LDL receptor expression via SREBP-2 activation, dramatically increasing clearance of LDL-cholesterol and VLDL remnants from the plasma. The statins mechanism of action also produces pleiotropic effects beyond LDL lowering: improved endothelial function (eNOS upregulation), anti-inflammatory effects (reduced CRP and IL-6), and atherosclerotic plaque stabilisation — effects attributed to reduced isoprenoid intermediates in the mevalonate pathway. These pleiotropic benefits may account for 15–25% of the cardiovascular risk reduction observed in landmark statin trials. The NCBI StatPearls chapter on HMG-CoA reductase inhibitors provides a comprehensive pharmacology reference.
CYP-mediated statin metabolism is clinically important because CYP3A4-metabolised statins (simvastatin, atorvastatin, lovastatin) are vulnerable to significant drug-drug interactions with CYP3A4 inhibitors, which can raise statin plasma concentrations 3–10-fold and precipitate severe myopathy or rhabdomyolysis. Hydrophilic statins with minimal CYP metabolism (rosuvastatin, pravastatin) are preferred when patients are taking strong CYP3A4 inhibitors. All statins are OATP1B1/1B3 substrates for hepatic uptake, making the CPIC statin pharmacogenomics guideline relevant for SLCO1B1 variant carriers at increased myopathy risk. See our CYP450 guide and FDA DDI table for interaction classification.
| Statin | Intensity (max dose) | LDL-C reduction (max dose) | CYP metabolism | Lipophilicity | Key interactions |
|---|---|---|---|---|---|
| Rosuvastatin | High (40 mg) | ~55% | Minimal (CYP2C9 minor) | Hydrophilic | OATP1B1 substrate; ciclosporin ↑ levels 7× |
| Atorvastatin | High (80 mg) | ~50% | CYP3A4 | Lipophilic | Clarithromycin, itraconazole, HIV PIs ↑ levels |
| Simvastatin | Moderate (40 mg) | ~38% | CYP3A4 (prodrug → active acid) | Lipophilic | Highest DDI risk; amiodarone max 10 mg; gemfibrozil contraindicated |
| Pravastatin | Moderate (40 mg) | ~32% | Minimal CYP; sulfation | Hydrophilic | Low DDI risk; safe in CYP3A4 inhibitor users |
| Fluvastatin | Moderate (80 mg XL) | ~33% | CYP2C9 | Lipophilic | Warfarin interaction (CYP2C9 inhibition); fluconazole ↑ levels |
| Lovastatin | Moderate (40 mg) | ~34% | CYP3A4 (prodrug) | Lipophilic | Grapefruit juice ↑ AUC 16×; similar to simvastatin DDI risk |
| Pitavastatin | Moderate (4 mg) | ~35% | Minimal (glucuronidation) | Lipophilic | Low DDI; may be preferred in complex polypharmacy patients |
Statins competitively inhibit HMG-CoA reductase, the enzyme that converts HMG-CoA to mevalonate — the rate-limiting step in hepatic cholesterol synthesis. Reduced intracellular cholesterol activates SREBP-2, which upregulates LDL receptor gene expression, increasing hepatocyte LDL-C and VLDL remnant clearance from plasma.
The mevalonate pathway also produces isoprenoids (farnesyl-PP, geranylgeranyl-PP), CoQ10, and dolichol. Isoprenoid depletion may underlie statin pleiotropic effects (anti-inflammatory, improved endothelial NO bioavailability) but also contributes to myopathy via impaired mitochondrial function. The clinical relevance of CoQ10 depletion for statin myalgia remains debated — supplementation trials have not consistently shown benefit. See our drug-induced nutrient depletion guide.
SREBP-2 activation increases LDL receptor density 2–4× on hepatocyte surfaces, dramatically increasing LDL-C and VLDL remnant clearance. This is the primary mechanism of LDL-C reduction and is enhanced by PCSK9 inhibitors, which prevent LDL receptor degradation.
Beyond LDL-C lowering: endothelial nitric oxide synthase (eNOS) upregulation, anti-inflammatory effects (↓ CRP, ↓ IL-6), stabilisation of atherosclerotic plaques, reduced platelet aggregation, and antioxidant effects. These may contribute ~15–25% of CV benefit independent of LDL-C reduction.
All statins require OATP1B1/1B3-mediated hepatic uptake for delivery to the liver. The SLCO1B1 c.521T>C variant (rs4149056) reduces hepatic uptake, increasing plasma statin concentrations and myopathy risk. CPIC recommends considering alternative statins for SLCO1B1 poor function carriers on high-dose simvastatin.
CYP2C9 poor metabolisers (fluvastatin, rosuvastatin) have higher statin exposure. SLCO1B1 c.521T>C (common — ~15% of Europeans are heterozygous) increases simvastatin acid AUC ~2× in heterozygotes, 4× in homozygotes. See our pharmacogenomics guide.
SAMD is classified by symptom severity and CK elevation. The vast majority of patients on statins tolerate them well — symptomatic myalgia occurs in ~5–10%, clinically significant CK elevation (>10× ULN) in <0.1%, and rhabdomyolysis in ~1–3 per 100,000 patient-years.
| Category | CK level | Symptoms | Action |
|---|---|---|---|
| Myalgia | Normal (<3× ULN) | Muscle pain/weakness | Exclude hypothyroidism, vitamin D deficiency; consider switch to hydrophilic statin or lower dose |
| Myopathy | 3–10× ULN | Muscle pain + weakness | Withhold statin; recheck CK; exclude drug interactions; restart at lower dose or alternate statin when resolved |
| Severe myopathy | 10–40× ULN | Significant weakness | Stop statin; urgent assessment; monitor renal function (myoglobinuria risk) |
| Rhabdomyolysis | >40× ULN + myoglobinuria | Severe pain, dark urine, AKI | Hospitalise; IV fluid resuscitation; monitor creatinine; consider renal replacement if oliguric AKI |
| SAAM (autoimmune) | Persistently elevated even after statin stopped | Proximal myopathy | Anti-HMGCR antibody; rheumatology referral; IVIG/immunosuppression |