EZETIMIBE AND SIMVASTATIN
Clinical safety rating: avoid
Strong CYP3A4 inhibitors (eg itraconazole) can significantly increase levels and risk of myopathy Can cause myopathy and rhabdomyolysis.
Ezetimibe inhibits intestinal cholesterol absorption by binding to the Niemann-Pick C1-Like 1 (NPC1L1) transporter at the brush border of enterocytes, reducing delivery of cholesterol to the liver. Simvastatin competitively inhibits HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, leading to upregulation of LDL receptors and increased clearance of LDL from plasma.
| Metabolism | Simvastatin is a prodrug that is metabolized via CYP3A4 to active metabolites; ezetimibe undergoes glucuronidation (UGT1A1, UGT1A3) to active ezetimibe-glucuronide with minor CYP-mediated metabolism. |
| Excretion | Ezetimibe is primarily excreted in feces (78%) as unchanged drug and glucuronide conjugate, with minimal renal excretion (11%). Simvastatin is excreted via biliary/fecal route (60%) as active metabolites and unchanged drug; renal excretion accounts for approximately 13% of the dose. |
| Half-life | Ezetimibe: terminal half-life is approximately 22 hours for ezetimibe and its glucuronide conjugate, allowing once-daily dosing. Simvastatin: terminal half-life is about 2-3 hours for the active metabolite, but the prodrug simvastatin has a shorter half-life (~2 hours); clinical effect persists due to inhibition of HMG-CoA reductase. |
| Protein binding | Ezetimibe: >90% bound to plasma proteins. Simvastatin: ~95% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Ezetimibe: Vd is approximately 10-20 L/kg, indicating extensive tissue distribution. Simvastatin: Vd is about 1.8-3.4 L/kg, reflecting moderate tissue distribution. |
| Bioavailability | Oral bioavailability: Ezetimibe is rapidly absorbed, with absolute bioavailability unknown; it undergoes extensive glucuronidation, and systemic exposure of active glucuronide is higher. Simvastatin: oral bioavailability is <5% due to extensive first-pass metabolism. Food does not affect absorption. |
| Onset of Action | Oral: Onset of lipid-lowering effect is observed within 2 weeks, with maximal effect at 4 weeks. |
| Duration of Action | Dosing interval is 24 hours; lipid-lowering effect persists throughout the dosing interval. After discontinuation, effects diminish over several weeks. |
| Molecular Weight | Ezetimibe: 409.43 Da; Simvastatin: 418.57 Da |
10 mg ezetimibe / 20 mg simvastatin orally once daily in the evening, with or without food; may titrate up to maximum of 10 mg ezetimibe / 40 mg simvastatin once daily; avoid doses >40 mg simvastatin unless already tolerated for ≥12 months.
| Dosage form | TABLET |
| Renal impairment | For eGFR <30 mL/min/1.73 m²: avoid simvastatin doses >20 mg daily; for eGFR 30-59 mL/min/1.73 m²: no dose adjustment required. Contraindicated in patients with active hepatic disease or unexplained persistent transaminase elevations. |
| Liver impairment | Contraindicated in Child-Pugh Class C; no specific recommendations for Child-Pugh A or B; use with caution and monitor liver enzymes. Discontinue if transaminases exceed 3 times upper limit of normal persistently. |
| Pediatric use | For heterozygous familial hypercholesterolemia (HeFH) in adolescents (10-17 years): starting dose 10 mg ezetimibe / 10 mg simvastatin orally once daily in the evening; may titrate every 4 weeks based on response and tolerability; maximum 10 mg ezetimibe / 40 mg simvastatin daily. Not recommended in children <10 years. |
| Geriatric use | No specific dose adjustment required; initiate at lower end of dosing range due to increased risk of myopathy and renal impairment; monitor renal function and muscle symptoms. |
| 1st trimester | Contraindicated: Simvastatin is FDA pregnancy category X; ezetimibe category C. Risk of fetal harm due to inhibition of cholesterol synthesis. |
| 2nd trimester | Contraindicated: Same risks as T1; avoid use. |
| 3rd trimester | Contraindicated: Risk of fetal harm continues; avoid use. |
Clinical note
Strong CYP3A4 inhibitors (eg itraconazole) can significantly increase levels and risk of myopathy Can cause myopathy and rhabdomyolysis.
| FDA category | Contraindicated |
| Placental transfer | Simvastatin crosses the placenta; ezetimibe likely crosses based on animal data. |
| Breastfeeding | Both ezetimibe and simvastatin are excreted in human milk. Simvastatin is contraindicated in breastfeeding due to potential for serious adverse reactions in nursing infants. Ezetimibe use is not recommended. |
■ FDA Black Box Warning
Simvastatin component: Increased risk of myopathy/rhabdomyolysis when used with certain drugs (e.g., cyclosporine, danazol, gemfibrozil, certain antifungals, macrolide antibiotics, and protease inhibitors). Avoid use with potent CYP3A4 inhibitors.
| Common Effects | Headache |
| Serious Effects |
Active liver disease or unexplained persistent elevations in serum transaminasesPregnancyBreastfeedingConcomitant use with strong CYP3A4 inhibitors (e.g., itraconazole, ketoconazole, posaconazole, voriconazole, HIV protease inhibitors, boceprevir, telaprevir, erythromycin, clarithromycin, telithromycin, nefazodone, cobicistat-containing products)Concomitant use with gemfibrozil, cyclosporine, or danazol
| Precautions | Myopathy/rhabdomyolysis risk increased with higher doses and interacting drugs, Hepatic effects: monitor liver enzymes; excessive alcohol use or liver disease, Cholelithiasis and biliary obstruction: ezetimibe may increase cholesterol in bile, Pancreatitis: reported during simvastatin therapy |
Loading safety data…
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | Pregnancy Category X. Ezetimibe and simvastatin are contraindicated in pregnancy. Statins inhibit HMG-CoA reductase, essential for fetal cholesterol synthesis, which is critical for normal fetal development. First trimester exposure may increase risk of congenital anomalies, including CNS and limb defects. Second and third trimester exposure may impair fetal growth and development. Both drugs cross the placenta. Use is contraindicated throughout pregnancy. |
| Fetal Monitoring | Monitor liver function tests (LFTs) at baseline and periodically; creatine kinase (CK) if muscle symptoms occur; lipid profile to assess efficacy. In pregnancy, fetal monitoring includes ultrasound for growth and anatomy if inadvertent exposure occurs. Assess for congenital anomalies if first-trimester exposure. Monitor maternal renal function. |
| Fertility Effects | No specific studies on fertility effects of ezetimibe/simvastatin combination. Statins may reduce serum testosterone and affect sperm parameters in men; however, clinical significance is unclear. Ezetimibe has no known direct effects on fertility. Women of childbearing potential should use effective contraception during therapy. |
| Food/Dietary | Avoid grapefruit juice. Limit alcohol intake. Take with or without food; consistent administration with evening meal may improve compliance. |
| Clinical Pearls | Ezetimibe/simvastatin is used for primary hyperlipidemia and homozygous familial hypercholesterolemia. Simvastatin is a CYP3A4 substrate; avoid concurrent use with strong CYP3A4 inhibitors (e.g., itraconazole, ketoconazole, erythromycin, clarithromycin, telithromycin, HIV protease inhibitors, nefazodone). Limit simvastatin dose to 20 mg if used with amiodarone, verapamil, or diltiazem. Do not exceed 10 mg simvastatin with diltiazem. Avoid grapefruit juice. Monitor for myopathy/rhabdomyolysis, especially in elderly, renal impairment, or hypothyroidism. Check hepatic function before initiation and as clinically indicated. Pregnancy category X; contraindicated in active liver disease. |
| Patient Advice | Take exactly as prescribed, usually once daily in the evening with or without food. · Do not take with grapefruit juice. · Avoid alcohol consumption. · Report unexplained muscle pain, tenderness, or weakness, especially if accompanied by fever or malaise. · Inform your doctor of all medications, including prescription and over-the-counter, especially other cholesterol-lowering drugs, antifungals, antibiotics, and amiodarone. · This medication can cause birth defects; do not use if pregnant or planning to become pregnant. Use effective contraception. · It may take several weeks to see effect; continue medication even if feeling well. · Maintain a cholesterol-lowering diet while on this medication. |