Simvastatin

ZOCOR^® is indicated:

• To reduce the risk of total mortality by reducing risk of coronary heart disease death, non-fatal myocardial infarction and stroke, and the need for coronary and non-coronary revascularization procedures in adults with established coronary heart disease, cerebrovascular disease, peripheral vascular disease, and/or diabetes, who are at high risk of coronary heart disease events.
• As an adjunct to diet to reduce low-density lipoprotein cholesterol (LDL-C):
  • In adults with primary hyperlipidemia.
  • In adults and pediatric patients aged 10 years and older with heterozygous familial hypercholesterolemia (HeFH).
• As an adjunct to other LDL-C-lowering therapies to reduce LDL-C in adults with homozygous familial hypercholesterolemia (HoFH).
• As an adjunct to diet for the treatment of adults with:
  • Primary dysbetalipoproteinemia.
  • Hypertriglyceridemia.

2.1 Important Dosage and Administration Information

• ZOCOR is no longer marketed in the 5 mg and 80 mg strengths. For dosing with the 5 mg strength, use another simvastatin product.
• Take ZOCOR orally once daily in the evening.
• The maximum recommended dosage is ZOCOR 40 mg once daily [see Dosage and Administration (2.2, 2.3)]. An 80 mg daily dosage of ZOCOR is restricted to patients who have been taking simvastatin 80 mg daily chronically (e.g., for 12 months or more) without evidence of muscle toxicity [see Warnings and Precautions (5.1)].
• If as dose is missed, take the missed dose as soon as possible. Do not double the next dose.
• For patients that require a high-intensity statin or are unable to achieve their LDL-C goal receiving ZOCOR 40 mg daily, prescribe alternative LDL-C-lowering treatment.
• Assess LDL-C when clinically appropriate, as early as 4 weeks after initiating ZOCOR, and adjust the dosage if necessary.

2.2 Recommended Dosage in Adult Patients

The recommended dosage range of ZOCOR is 20 mg to 40 mg once daily.

2.3 Recommended Dosage in Pediatric Patients 10 Years of Age and Older with HeFH

The recommended dosage range of ZOCOR is 10 mg to 40 mg daily.

2.4 Recommended Dosage in Patients with Renal Impairment

For patients with severe renal impairment [creatinine clearance (CLcr) 15 – 29 mL/min], the recommended starting dosage of simvastatin is 5 mg once daily [see Warnings and Precautions (5.1) and Use in Specific Populations (8.6)]. Use another simvastatin product to initiate dosing in such patients [see Dosage and Administration (2.1)].

There are no dosage adjustment recommendations for patients with mild or moderate renal impairment.

2.5 Dosage Modifications Due to Drug Interactions

Concomitant use of ZOCOR with the following drugs requires dosage modification of ZOCOR [see Warnings and Precautions (5.1) and Drug Interactions (7.1)].

Patients taking Lomitapide

Reduce the dosage of ZOCOR by 50%. Do not exceed ZOCOR 20 mg once daily (or 40 mg once daily for patients who have previously taken an 80 mg daily dosage of ZOCOR chronically while taking lomitapide) [see Dosage and Administration (2.1)].

Patients taking Verapamil, Diltiazem, or Dronedarone

Do not exceed ZOCOR 10 mg once daily.

Patients taking Amiodarone, Amlodipine, or Ranolazine

Do not exceed ZOCOR 20 mg once daily.

ZOCOR tablets:

• 10 mg: peach, oval tablets, marked MSD 735 on one side and plain on the other
• 20 mg: tan, oval tablets, marked MSD 740 on one side and plain on the other
• 40 mg: brick red, oval tablets, marked MSD 749 on one side and plain on the other

The 5 mg and 80 mg strengths of ZOCOR are no longer marketed.

ZOCOR is contraindicated in the following conditions:

• Concomitant use of strong CYP3A4 inhibitors (select azole anti-fungals, macrolide antibiotics, anti-viral medications, and nefazodone) [see Drug Interactions (7.1)].
• Concomitant use of cyclosporine, danazol or gemfibrozil [see Drug Interactions (7.1)].
• Acute liver failure or decompensated cirrhosis [see Warnings and Precautions (5.3)].
• Hypersensitivity to simvastatin or any excipients in ZOCOR. Hypersensitivity reactions, including anaphylaxis, angioedema and Stevens-Johnson syndrome, have been reported [see Adverse Reactions (6.2)].

5.1 Myopathy and Rhabdomyolysis

ZOCOR may cause myopathy and rhabdomyolysis. Acute kidney injury secondary to myoglobinuria and rare fatalities have occurred as a result of rhabdomyolysis in patients treated with statins, including ZOCOR.

In clinical studies of 24,747 ZOCOR-treated patients with a median follow-up of 4 years, the incidence of myopathy, defined as unexplained muscle weakness, pain, or tenderness accompanied by creatinine kinase (CK) increases greater than ten times the upper limit of normal (10xULN), were approximately 0.03%, 0.08%, and 0.61% in patients treated with ZOCOR 20 mg, 40 mg, and 80 mg daily, respectively. In another clinical study of 12,064 ZOCOR-treated patients (with a history of myocardial infarction) with a mean follow-up of 6.7 years, the incidences of myopathy in patients taking ZOCOR 20 mg and 80 mg daily were approximately 0.02% and 0.9%, respectively. The incidences of rhabdomyolysis (defined as myopathy with a CK >40xULN) in patients taking ZOCOR 20 mg and 80 mg daily were approximately 0% and 0.4%, respectively [see Adverse Reactions (6.1)].

Risk Factors for Myopathy

Risk factors for myopathy include age 65 years or greater, uncontrolled hypothyroidism, renal impairment, concomitant use with certain other drugs (including other lipid-lowering therapies), and higher ZOCOR dosage; Chinese patients on ZOCOR may be at higher risk for myopathy [see Contraindications (4), Drug Interactions (7.1), and Use in Specific Populations (8.8)]. The risk of myopathy is increased by elevated plasma levels of simvastatin and simvastatin acid. The risk is also greater in patients taking an 80 mg daily dosage of ZOCOR compared with patients taking lower ZOCOR dosages and compared with patients using other statins with similar or greater LDL-C-lowering efficacy [see Adverse Reactions (6.1)].

Steps to Prevent or Reduce the Risk of Myopathy and Rhabdomyolysis

The concomitant use of strong CYP3A4 inhibitors with ZOCOR is contraindicated. If short-term treatment with strong CYP3A4 inhibitors is required, temporarily suspend ZOCOR during the duration of strong CYP3A4 inhibitor treatment. The concomitant use of ZOCOR with gemfibrozil, cyclosporine, or danazol is also contraindicated [see Contraindications (4) and Drug Interactions (7.1)].

ZOCOR dosage modifications are recommended for patients taking lomitapide, verapamil, diltiazem, dronedarone, amiodarone, amlodipine or ranolazine [see Dosage and Administration (2.5)]. ZOCOR use should be temporarily suspended in patients taking daptomycin. Lipid modifying doses (≥1 gram/day) of niacin, fibrates, colchicine, and grapefruit juice may also increase the risk of myopathy and rhabdomyolysis [see Drug Interactions (7.1)].

Use the 80 mg daily dosage of ZOCOR only in patients who have been taking simvastatin 80 mg daily chronically without evidence of muscle toxicity [see Dosage and Administration (2.1)]. If patients treated with an 80 mg daily dosage of ZOCOR are prescribed an interacting drug that increases the risk for myopathy and rhabdomyolysis, switch to an alternate statin [see Drug Interactions (7.1)].

Discontinue ZOCOR if markedly elevated CK levels occur or if myopathy is either diagnosed or suspected. Muscle symptoms and CK increases may resolve if ZOCOR is discontinued. Temporarily discontinue ZOCOR in patients experiencing an acute or serious condition at high risk of developing renal failure secondary to rhabdomyolysis, e.g., sepsis; shock; severe hypovolemia; major surgery; trauma; severe metabolic, endocrine, or electrolyte disorders; or uncontrolled epilepsy.

Inform patients of the risk of myopathy and rhabdomyolysis when starting or increasing the ZOCOR dosage and advise patients receiving an 80 mg daily dosage of ZOCOR of the increased risk of myopathy and rhabdomyolysis. Instruct patients to promptly report any unexplained muscle pain, tenderness or weakness, particularly if accompanied by malaise or fever.

5.2 Immune-Mediated Necrotizing Myopathy

There have been rare reports of immune-mediated necrotizing myopathy (IMNM), an autoimmune myopathy, associated with statin use, including reports of recurrence when the same or a different statin was administered. IMNM is characterized by proximal muscle weakness and elevated serum creatine kinase that persist despite discontinuation of statin treatment; positive anti-HMG CoA reductase antibody; muscle biopsy showing necrotizing myopathy without significant inflammation; and improvement with immunosuppressive agents. Additional neuromuscular and serologic testing may be necessary. Treatment with immunosuppressive agents may be required. Discontinue ZOCOR if IMNM is suspected.

5.3 Hepatic Dysfunction

Increases in serum transaminases have been reported with use of ZOCOR [see Adverse Reactions (6.1)]. In most cases, these changes appeared soon after initiation, were transient, were not accompanied by symptoms, and resolved or improved on continued therapy or after a brief interruption in therapy. Persistent increases to more than 3xULN in serum transaminases have occurred in approximately 1% of patients receiving ZOCOR in clinical studies. Marked persistent increases of hepatic transaminases have also occurred with ZOCOR. There have been rare postmarketing reports of fatal and non-fatal hepatic failure in patients taking statins, including ZOCOR.

Patients who consume substantial quantities of alcohol and/or have a history of liver disease may be at increased risk for hepatic injury.

Consider liver enzyme testing before ZOCOR initiation and when clinically indicated thereafter. ZOCOR is contraindicated in patients with acute liver failure or decompensated cirrhosis [see Contraindications (4)]. If serious hepatic injury with clinical symptoms and/or hyperbilirubinemia or jaundice occurs, promptly discontinue ZOCOR.

5.4 Increases in HbA1c and Fasting Serum Glucose Levels

Increases in HbA1c and fasting serum glucose levels have been reported with statins, including ZOCOR. Optimize lifestyle measures, including regular exercise, maintaining a healthy body weight, and making healthy food choices.

The following important adverse reactions are described below and elsewhere in the labeling:

• Myopathy and Rhabdomyolysis [see Warnings and Precautions (5.1)]
• Immune-Mediated Necrotizing Myopathy [see Warnings and Precautions (5.2)]
• Hepatic Dysfunction [see Warnings and Precautions (5.3)]
• Increases in HbA1c and Fasting Serum Glucose Levels [see Warnings and Precautions (5.4)]

6.1 Clinical Trials Experience

Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.

In clinical studies, 2,423 adult patients were exposed to ZOCOR with a median duration of follow-up of approximately 18 months. The most commonly reported adverse reactions (incidence ≥5%) in these ZOCOR clinical studies were: upper respiratory infections (9%), headache (7%), abdominal pain (7%), constipation (7%), and nausea (5%). Overall, 1.4% of patients discontinued ZOCOR due to adverse reactions. The most common adverse reactions that led to discontinuation were: gastrointestinal disorders (0.5%), myalgia (0.1%), and arthralgia (0.1%).

In a Cardiovascular Outcomes Study (the Scandinavian Simvastatin Survival Study [Study 4S]), adult patients (age range 35-71 years, 19% women, 100% Caucasians) were treated with 20-40 mg per day of ZOCOR or placebo over a median of 5.4 years [see Clinical Studies (14)]; adverse reactions reported in ≥2% of patients and at a rate greater than placebo are shown in Table 1.

Myopathy/Rhabdomyolysis

In clinical studies with a median follow-up of at least 4 years, in which 24,747 patients received ZOCOR , the incidence of myopathy (defined as unexplained muscle weakness, pain, or tenderness accompanied by CK increases greater than 10xULN) was approximately 0.03%, 0.08%, and 0.61% for the ZOCOR 20 mg, 40 mg, and 80 mg daily groups, respectively.

In a clinical outcomes study in which 12,064 adult patients with a history of myocardial infarction were treated with ZOCOR (mean follow-up 6.7 years), the incidence of myopathy (defined as unexplained muscle weakness or pain with a serum CK >10x [1200 U/L] ULN) in patients taking ZOCOR 20 mg and 80 mg daily was approximately 0.02% and 0.9%, respectively. The incidence of rhabdomyolysis (defined as myopathy with a CK >40xULN) in patients on ZOCOR 20 mg and 80 mg daily was approximately 0% and 0.4%, respectively. The incidence of myopathy and rhabdomyolysis were highest during the first year and then decreased during the subsequent years of treatment.

In another clinical outcomes study in which 10,269 adult patients were treated with ZOCOR 40 mg per day (mean follow-up of 5 years), the incidence of myopathy/rhabdomyolysis was <0.1% in patients treated with ZOCOR.

Elevations in Liver Enzyme Tests

Moderate (less than 3xULN) elevations of serum transaminases have been reported with use of ZOCOR.

Persistent increases to more than 3xULN in serum transaminases have occurred in approximately 1% of patients receiving ZOCOR in clinical studies. Marked persistent increases of hepatic transaminases have occurred with ZOCOR. Elevated alkaline phosphatase and γ-glutamyl transpeptidase have also been reported.

In Study 4S, with a median follow-up of 5.4 years, 1,986 adult patients were treated with ZOCOR 20 mg once daily, of whom 37% titrated to 40 mg once daily. The percentage of patients with one or more occurrences of transaminase elevations to >3xULN was 0.7% in patients taking ZOCOR compared with 0.6% in patients taking placebo. Elevated transaminases leading to discontinuation of study treatment occurred in 0.4% of patients taking ZOCOR and 0.2% of patients taking placebo. The majority of elevated transaminases leading to treatment discontinuation occurred within in the first year.

Adverse Reactions in Pediatric Patients with Heterozygous Familial Hypercholesterolemia

In a 48-week clinical study in pediatric patients 10 years of age and older (43% female, 97.7% Caucasians, 1.7% Hispanics, 0.6% Multiracial) with HeFH (n=175), treated with placebo or ZOCOR (10-40 mg daily), the most common adverse reactions were upper respiratory infection, headache, abdominal pain, and nausea [see Use in Specific Populations (8.4) and Clinical Studies (14)].

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of ZOCOR. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as whole: fever, chills, malaise, asthenia

Blood and Lymphatic System Disorders: anemia, thrombocytopenia, leukopenia, hemolytic anemia, positive ANA, ESR increase, eosinophilia

Gastrointestinal Disorders: pancreatitis, vomiting

Hepatic and Pancreatic Disorders: hepatitis/jaundice, fatal and non-fatal hepatic failure

Immune System Disorders: hypersensitivity syndrome including: anaphylaxis, angioedema, lupus erythematous-like syndrome, dermatomyositis, vasculitis

Musculoskeletal and Connective Tissue Disorders: muscle cramps, immune-mediated necrotizing myopathy, polymyalgia rheumatica, arthritis

Nervous System Disorders: dizziness, depression, paresthesia, peripheral neuropathy. Rare reports of cognitive impairment (e.g., memory loss, forgetfulness, amnesia, memory impairment, confusion) associated with statin use. Cognitive impairment was generally nonserious, and reversible upon statin discontinuation, with variable times to symptom onset (1 day to years) and symptom resolution (median of 3 weeks). There have been rare reports of new-onset or exacerbation of myasthenia gravis, including ocular myasthenia, and reports of recurrence when the same or a different statin was administered.

Skin and Subcutaneous Tissue Disorders: pruritus, alopecia, a variety of skin changes (e.g., nodules, discoloration, dryness of skin/mucous membranes, changes to hair/nails), purpura, lichen planus, urticaria, photosensitivity, flushing, toxic epidermal necrolysis, erythema multiforme, including Stevens-Johnson syndrome

Respiratory and Thoracic: interstitial lung disease, dyspnea

Reproductive System Disorders: erectile dysfunction

7.1 Drug Interactions that Increase the Risk of Myopathy and Rhabdomyolysis with ZOCOR

ZOCOR is a substrate of CYP3A4 and of the transport protein OATP1B1. ZOCOR exposure can be significantly increased with concomitant administration of inhibitors of CYP3A4 and OATP1B1. Table 2 includes a list of drugs that increase the risk of myopathy and rhabdomyolysis when used concomitantly with ZOCOR and instructions for preventing or managing them [see Warnings and Precautions (5.1) and Clinical Pharmacology (12.3)].

7.2 ZOCOR Effects on Other Drugs

Table 3 presents ZOCOR’s effect on other drugs and instructions for preventing or managing them.

8.1 Pregnancy

Risk Summary

Discontinue ZOCOR when pregnancy is recognized. Alternatively, consider the ongoing therapeutic needs of the individual patient.

ZOCOR decreases synthesis of cholesterol and possibly other biologically active substances derived from cholesterol; therefore, ZOCOR may cause fetal harm when administered to pregnant patients based on the mechanism of action [see Clinical Pharmacology (12.1)]. In addition, treatment of hyperlipidemia is not generally necessary during pregnancy. Atherosclerosis is a chronic process and the discontinuation of lipid-lowering drugs during pregnancy should have little impact on the outcome of long-term therapy of primary hyperlipidemia for most patients.

Available data from case series and prospective and retrospective observational cohort studies over decades of use with statins in pregnant women have not identified a drug-associated risk of major congenital malformations. Published data from prospective and retrospective observational cohort studies with ZOCOR use in pregnant women are insufficient to determine if there is a drug-associated risk of miscarriage (see Data ).

In animal reproduction studies, no adverse developmental effects were observed in pregnant rats or rabbits orally administered simvastatin during the period of organogenesis at doses that resulted in 2.5 and 2 times, respectively, the human exposure at the maximum recommended human dosage of 80 mg/day, based on body surface area (mg/m²) (see Data ).

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.

Data

Human Data

A Medicaid cohort linkage study of 1152 statin-exposed pregnant women compared to 886,996 controls did not find a significant teratogenic effect from maternal use of statins in the first trimester of pregnancy, after adjusting for potential confounders – including maternal age, diabetes mellitus, hypertension, obesity, and alcohol and tobacco use – using propensity score-based methods. The relative risk of congenital malformations between the group with statin use and the group with no statin use in the first trimester was 1.07 (95% confidence interval 0.85 to 1.37) after controlling for confounders, particularly pre-existing diabetes mellitus. There were also no statistically significant increases in any of the organ-specific malformations assessed after accounting for confounders. In the majority of pregnancies, statin treatment was initiated prior to pregnancy and was discontinued at some point in the first trimester when pregnancy was identified. Study limitations include reliance on physician coding to define the presence of a malformation, lack of control for certain confounders such as body mass index, use of prescription dispensing as verification for the use of a statin, and lack of information on non-live births.

Animal Data

Simvastatin was given to pregnant rats at doses of 6.25, 12.5 and 25 mg/kg/day (0.6 times, 1.3 times, and 2.5 times, respectively, the maximum recommended dosage of 80 mg/day when normalized to body surface area) from gestation days 6-17 and to pregnant rabbits from gestation days 6-18 at doses of 2.5, 5, and 10 mg/kg/day (0.5 times, 1 times, and 2 times, respectively, the maximum recommended dosage of 80 mg/day when normalized to body surface area). For both species, there was no evidence of maternal toxicity or embryolethality. In rats, mean fetal body weights in the 25 mg/kg/day group were decreased 5.4%. Similar fetal body weight effects were not observed in rabbits.

Simvastatin doses of 6.25, 12.5 and 25 mg/kg/day (0.6 times, 1.3 times, and 2.5 times, respectively, the maximum recommended dosage of 80 mg/day when normalized to body surface area) were given to pregnant rats from gestation day 15 to lactation day 21. Slight decreases in maternal body weight gain and pup postnatal day 0 weight were observed in the 25 mg/kg/day dose group. Mean body weight gain of pups during lactation was slightly decreased at doses ≥12.5 mg/kg/day. Post weaning weight, behavior, reproductive performance and fertility of the offspring were not affected at any dose tested.

Placental transfer of simvastatin was not evaluated in rats or rabbits. However, it has been shown that other drugs in this class cross the placenta.

8.2 Lactation

Risk Summary

There is no information about the presence of simvastatin in human or animal milk, the effects of the drug on the breastfed infant or the effects of the drug on milk production. However, it has been shown that another drug in this class passes into human milk. Statins, including ZOCOR, decrease cholesterol synthesis and possibly the synthesis of other biologically active substances derived from cholesterol and may cause harm to the breastfed infant.

Because of the potential for serious adverse reactions in a breastfed infant, based on the mechanism of action, advise patients that breastfeeding is not recommended during treatment with ZOCOR [see Use in Specific Populations (8.1), Clinical Pharmacology (12.1)].

8.4 Pediatric Use

The safety and effectiveness of ZOCOR as an adjunct to diet to reduce LDL-C have been established in pediatric patients 10 years of age and older with HeFH. Use of ZOCOR for this indication is based on a double-blind, placebo-controlled clinical study in 175 pediatric patients (99 boys and 76 girls at least 1 year post-menarche) 10 years of age and older with HeFH. In this limited controlled study, there was no significant effect on growth or sexual maturation in the boys or girls, or on menstrual cycle length in girls.

The safety and effectiveness of ZOCOR have not been established in pediatric patients younger than 10 years of age with HeFH or in pediatric patients with other types of hyperlipidemia (other than HeFH).

8.5 Geriatric Use

Of the total number of ZOCOR-treated patients in clinical studies 1,021 (23%) patients, 5,366 (52%) patients, and 363 (15%) patients were ≥65 years old, respectively. In Study HPS, 615 (6%) patients were ≥75 years old [see Clinical Studies (14)]. In a clinical study of patients treated with ZOCOR 80 mg daily, patients ≥65 years of age had an increased risk of myopathy, including rhabdomyolysis, compared to patients <65 years of age.

A pharmacokinetic study with ZOCOR use showed the mean plasma level of total inhibitors to be approximately 45% higher in geriatric patients between 70-78 years of age compared with patients between 18-30 years of age [see Clinical Pharmacology (12.3)].

Advanced age (≥65 years) is a risk factor for ZOCOR-associated myopathy and rhabdomyolysis. Dose selection for an elderly patient should be cautious, recognizing the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy and the higher risk of myopathy. Monitor geriatric patients receiving ZOCOR for the increased risk of myopathy [see Warnings and Precautions (5.1)].

8.6 Renal Impairment

Renal impairment is a risk factor for myopathy and rhabdomyolysis. Monitor all patients with renal impairment for development of myopathy. In patients with severe renal impairment (CLcr 15 – 29 mL/min), the recommended starting dosage is simvastatin 5 mg once daily [see Dosage and Administration (2.4), Warnings and Precautions (5.1)]. The 5 mg strength of ZOCOR is no longer marketed. Use another simvastatin product to initiate dosing in such patients.

8.7 Hepatic Impairment

ZOCOR is contraindicated in patients with acute liver failure or decompensated cirrhosis [see Contraindications (4), Warnings and Precautions (5.3)].

8.8 Chinese Patients

In a clinical study in which patients at high risk of CVD were treated with simvastatin 40 mg/day (median follow-up 3.9 years), the incidence of myopathy was approximately 0.05% for non-Chinese patients (n=7367) compared with 0.24% for Chinese patients (n=5468). In this study, the incidence of myopathy for Chinese patients on simvastatin 40 mg/day or ezetimibe/simvastatin 10/40 mg/day coadministered with extended-release niacin 2 g/day was 1.24%.

Chinese patients may be at higher risk for myopathy, monitor these patients appropriately. Coadministration of ZOCOR with lipid-modifying doses of niacin-containing products (≥1 g/day niacin) is not recommended in Chinese patients [see Warnings and Precautions (5.1), Drug Interactions (7.1)].

No specific antidotes for ZOCOR are known. Contact Poison Control (1-800-222-1222) for latest recommendations.

12.1 Mechanism of Action

Simvastatin is a prodrug and is hydrolyzed to its active β-hydroxyacid form, simvastatin acid, after administration. Simvastatin acid and its metabolites are inhibitors of HMG-CoA reductase, the rate-limiting enzyme that converts HMG-CoA to mevalonate, a precursor of cholesterol.

12.2 Pharmacodynamics

Inhibition of HMG-CoA reductase by simvastatin acid accelerates the expression of LDL-receptors, followed by the uptake of LDL-C from blood to the liver, leading to a decrease in plasma LDL-C and total cholesterol. Sustained inhibition of cholesterol synthesis in the liver also decreases levels of very-low-density lipoproteins. The maximum LDL-C reduction of ZOCOR is usually achieved by 4 weeks and is maintained after that.

12.3 Pharmacokinetics

Simvastatin is a lactone that is readily hydrolyzed in vivo to the corresponding β-hydroxyacid. Pharmacokinetics (PK) of simvastatin and its metabolites was originally characterized using inhibition of HMG-CoA reductase activity following base hydrolysis of plasma samples, as specific bioanalytical methods were not available. Inhibition of the enzyme activity (equivalent to the level of total inhibitors) represented the combination of activities in plasma following administration of simvastatin from both active (simvastatin acid and its metabolites) and latent forms (simvastatin and its metabolites) after conversion to the active forms in the presence of base.

Absorption

Following an oral dose of ¹⁴C-labeled simvastatin, plasma concentrations of total radioactivity (simvastatin plus ¹⁴C-metabolites) peaked at 4 hours and declined rapidly to about 10% of peak by 12 hours postdose. Since simvastatin undergoes extensive first-pass extraction in the liver, the availability of simvastatin to the general circulation is low (<5%). PK, assessed as area under the concentrations of total inhibitors – time curve, was apparently linear with doses up to 120 mg.

Effect of Food

The plasma profile of total inhibitors concentration was not affected when simvastatin was administered with low fat meal.

Distribution

Both simvastatin and its β-hydroxyacid metabolite are highly bound (approximately 95%) to human plasma proteins.

Elimination

Metabolism

Simvastatin is metabolized by CYP3A4. The major active metabolites of simvastatin present in human plasma are simvastatin acid and its 6′-hydroxy, 6′-hydroxymethyl, and 6′-exomethylene derivatives. Peak plasma concentrations of both active and total inhibitors were attained within 1.3 to 2.4 hours postdose.

Excretion

Following an oral dose of ¹⁴C-labeled simvastatin, 13% of the dose was excreted in urine and 60% in feces.

Specific Populations

Geriatric Patients

In a study including 16 geriatric patients between 70 and 78 years of age who received ZOCOR 40 mg/day, the mean plasma level of total inhibitors was increased approximately 45% compared with 18 patients between 18-30 years of age [see Use in Specific Populations (8.5)].

Drug Interaction Studies

Simvastatin acid is a substrate of the transport protein OATP1B1. Concomitant administration of inhibitors of the transport protein OATP1B1 and/or CYP3A4 may lead to increased exposure of simvastatin acid. Cyclosporine has been shown to increase the AUC of statins; although the mechanism is not fully understood, the increase in AUC for simvastatin acid is presumably due, in part, to inhibition of CYP3A4 and/or OATP1B1 [see Drug Interactions (7)].

Table 4 displays the effect of coadministered drugs or grapefruit juice on simvastatin systemic exposure [see Drug Interactions (7)].

• ¹ Results based on a chemical assay except results with propranolol as indicated.
• ² Results could be representative of the following CYP3A4 inhibitors: ketoconazole, erythromycin, clarithromycin, HIV protease inhibitors, and nefazodone.
• ³ Simvastatin acid refers to the β-hydroxyacid of simvastatin.
• ⁴ The effect of amounts of grapefruit juice between those used in these two studies on simvastatin pharmacokinetics has not been studied.
• ⁵ Double-strength: one can of frozen concentrate diluted with one can of water. Grapefruit juice was administered TID for 2 days, and 200 mL together with single dose simvastatin and 30 and 90 minutes following single dose simvastatin on Day 3.
• ⁶ Single-strength: one can of frozen concentrate diluted with 3 cans of water. Grapefruit juice was administered with breakfast for 3 days, and simvastatin was administered in the evening on Day 3.

ZOCOR’s Effect on the Pharmacokinetics of Other Drugs

In a study of 12 healthy volunteers, simvastatin at the 80-mg dose had no effect on the metabolism of the probe cytochrome P450 isoform 3A4 (CYP3A4) substrates midazolam and erythromycin. Simvastatin is not an inhibitor of CYP3A4 and is not expected to affect the plasma levels of other drugs metabolized by CYP3A4.

Coadministration of simvastatin (40 mg QD for 10 days) resulted in an increase in the maximum mean levels of cardioactive digoxin (given as a single 0.4 mg dose on day 10) by approximately 0.3 ng/mL [see Drug Interactions (7.2)].

ZOCOR tablets are supplied as follows:

• ¹ The 5 mg and 80 mg strengths of ZOCOR are no longer marketed.

Storage

Store between 41°F to 86°F (5°C to 30°C).