Simvastatin

Generic Name: Simvastatin

Brand Names: Zocor

Simvastatin is a statin medication used to lower cholesterol and reduce cardiovascular risk.

CardiovascularStatinsCholesterol

Drug Class

HMG-CoA Reductase Inhibitor (Statin)

Pregnancy

Contraindicated in pregnancy (Category X). Cholesterol and its biosynthesis products are essential for fetal development. Statins may cause fetal harm. Women of childbearing potential must use effective contraception. Discontinue immediately if pregnancy is detected.

Available Forms

5 mg oral tablet, 10 mg oral tablet, 20 mg oral tablet, 40 mg oral tablet, 80 mg oral tablet (restricted use)

What It's Used For

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Condition	Starting Dose	Maintenance Dose
Hyperlipidemia / Atherosclerotic CVD risk reduction	10-20 mg once daily in the evening	20-40 mg once daily in the evening; 80 mg dose restricted to patients who have tolerated it for 12+ months without myopathy
Homozygous Familial Hypercholesterolemia	40 mg once daily in the evening	40 mg daily (or 80 mg in 3 divided doses: 20 mg, 20 mg, 40 mg evening)
Adolescents (10-17 years, heterozygous FH)	10 mg once daily in the evening	10-40 mg once daily in the evening; maximum 40 mg/day

Side Effects

Common Side Effects:

Headache
Constipation
Nausea
Abdominal pain
Upper respiratory infections
Myalgia

Serious Side Effects:

Rhabdomyolysis
Myopathy
Hepatotoxicity
Immune-mediated necrotizing myopathy
New-onset diabetes

Drug Interactions

Strong CYP3A4 inhibitors (itraconazole, ketoconazole, clarithromycin, HIV protease inhibitors): Contraindicated with simvastatin. These dramatically increase simvastatin blood levels, greatly raising the risk of rhabdomyolysis.
Amiodarone: Simvastatin dose must not exceed 20 mg daily when co-administered with amiodarone due to significantly increased myopathy risk.
Amlodipine and diltiazem: Simvastatin dose must not exceed 20 mg daily when combined with either of these calcium channel blockers due to CYP3A4 inhibition.
Gemfibrozil (and other fibrates): Concurrent use significantly increases the risk of rhabdomyolysis. Gemfibrozil is contraindicated with simvastatin. Fenofibrate is preferred if combination therapy is required.
Grapefruit juice: Large quantities (more than 1 quart daily) inhibit CYP3A4 and can increase simvastatin levels. Patients should avoid consuming large amounts of grapefruit juice.
Warfarin: Simvastatin may potentiate the anticoagulant effect of warfarin. Monitor INR when starting or adjusting simvastatin dose.

Additional Information

Simvastatin is an HMG-CoA reductase inhibitor (statin) used to treat hyperlipidemia and reduce cardiovascular risk. It was one of the first statins introduced and remains widely used for its proven efficacy in preventing cardiovascular events.

Mechanism of Action

Simvastatin inhibits cholesterol synthesis:

Prodrug conversion: Lactone form converted to active hydroxy acid form
HMG-CoA reductase inhibition: Blocks the rate-limiting step in cholesterol biosynthesis
Upregulates LDL receptors: Compensatory response to reduced hepatic cholesterol increases LDL clearance
Reduces LDL cholesterol: 27-47% reduction depending on dose
Pleiotropic effects: Anti-inflammatory, antithrombotic, and endothelial benefits

Available Formulations

Simvastatin is available as tablets:

5 mg, 10 mg, 20 mg, 40 mg, 80 mg tablets

Also available in combination with ezetimibe (Vytorin).

Medical Uses

FDA-Approved Indications:

Hyperlipidemia: Reduces total cholesterol, LDL-C, apoB, and triglycerides; increases HDL-C
Prevention of cardiovascular events in patients with coronary heart disease or at high cardiovascular risk
Homozygous familial hypercholesterolemia
Heterozygous familial hypercholesterolemia in adolescents 10-17 years

Dosing Guidelines

Adults (General Hyperlipidemia):

Initial: 10-20 mg once daily in the evening
Range: 5-40 mg daily
Maximum: 40 mg daily (80 mg restricted to patients who have taken it for ≥12 months without muscle problems)

High Cardiovascular Risk:

20-40 mg once daily in the evening

Pediatric (Heterozygous FH, 10-17 years):

Initial: 10 mg once daily in the evening
Range: 10-40 mg daily

Timing:

Take in the evening (cholesterol synthesis peaks at night)

Important Safety Information

80 mg Dose Restriction:

80 mg should not be started in new patients
Only continue 80 mg in patients who have been stable on this dose for ≥12 months without evidence of muscle toxicity

Contraindications:

Active liver disease or unexplained persistent transaminase elevations
Pregnancy and breastfeeding
Concomitant use with strong CYP3A4 inhibitors, gemfibrozil, cyclosporine, danazol

Warnings and Precautions:

Myopathy/Rhabdomyolysis: Risk dose-related; higher risk at 80 mg
Hepatotoxicity: Monitor liver enzymes
Diabetes: May increase HbA1c and fasting glucose

Drug Interactions

Contraindicated Combinations:

Strong CYP3A4 inhibitors (itraconazole, ketoconazole, posaconazole, HIV protease inhibitors, boceprevir, telaprevir, erythromycin, clarithromycin, telithromycin, nefazodone, cobicistat)
Gemfibrozil, cyclosporine, danazol

Dose Limitations:

Amiodarone, dronedarone, amlodipine, ranolazine: Max 20 mg simvastatin
Diltiazem, verapamil: Max 10 mg simvastatin
Lomitapide: Max 20 mg simvastatin

Other:

Warfarin: Monitor INR
Grapefruit juice: Avoid large quantities

Special Populations

Hepatic Impairment: Contraindicated in active liver disease
Renal Impairment: Start 5 mg for severe impairment; use caution with doses >10 mg
Pregnancy: Contraindicated (Category X)
Lactation: Contraindicated
Elderly: No specific adjustment; start conservatively
Chinese descent: Avoid simvastatin 80 mg (increased myopathy risk with niacin)

Frequently Asked Questions

The body produces most of its cholesterol at night. Simvastatin has a relatively short half-life (about 2-3 hours for the active form), so taking it in the evening ensures peak drug levels coincide with peak cholesterol production, maximizing its effectiveness. Extended-release formulations of other statins (like rosuvastatin or atorvastatin) with longer half-lives do not have this timing requirement.

The FDA restricted the 80 mg dose in 2011 because clinical data showed a significantly higher risk of muscle damage (myopathy and rhabdomyolysis) at this dose compared to lower doses. The 80 mg dose should only be used in patients who have already taken it for 12 months or more without muscle problems. New patients should not be started on 80 mg.

Contact your doctor immediately if you experience unexplained muscle pain, tenderness, or weakness, especially if accompanied by fever, dark-colored urine, or general malaise. These can be signs of myopathy or the more serious rhabdomyolysis, where muscle tissue breaks down and can damage the kidneys.

Small amounts of grapefruit (like half a grapefruit or a small glass of juice) are unlikely to cause significant problems. However, consuming large quantities regularly can inhibit the enzyme that metabolizes simvastatin, potentially increasing drug levels and the risk of side effects. Many doctors recommend avoiding grapefruit products altogether for simplicity.

Statins manage cholesterol levels but do not cure the underlying metabolic tendency toward high cholesterol. Stopping the medication typically causes cholesterol to return to pre-treatment levels. For most patients with cardiovascular risk, lifelong therapy is recommended. Your doctor will weigh your ongoing risk factors to determine the best plan.

Simvastatin can cause mild elevations in liver enzymes (ALT/AST), usually within the first few months of therapy. Clinically significant liver injury is rare. Routine periodic liver function testing is no longer universally recommended by guidelines but your doctor may check liver enzymes before starting and as clinically indicated.

Questions to Ask Your Doctor

Consider discussing these topics at your next appointment:

✓Are any of my current medications known to interact with simvastatin and require a dose limitation?
✓Should I have baseline liver function and creatine kinase levels checked before starting?
✓Is simvastatin the best statin choice for me, or would a statin without CYP3A4 metabolism (like rosuvastatin) be safer given my other medications?
✓What LDL cholesterol target am I aiming for based on my cardiovascular risk?

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Related Health Conditions

This medication is commonly used to treat or manage the following conditions:

Stroke

A stroke, caused by interrupted brain blood supply from blockage (ischemic) or bleeding (hemorrhagic), is a medical emergency requiring prompt treatment to minimize brain damage.

Learn More

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.