Simvastat

Uses

Primary hypercholesterolemia (type IIa and IIb) in patients who have not responded adequately to diet and other appropriate measures. Coronary heart disease and elevated plasma cholesterol level.

Simvastat is also used to associated treatment for these conditions: Cardiovascular Events, Diabetes Mellitus, Heterozygous Familial Hypercholesterolemia, High Cholesterol, Homozygous Familial Hypercholesterolemia, Mixed Hyperlipidemia, History of coronary heart disease cardiovascular event, History of stroke or other cerebrovascular disease cardiovascular event

How Simvastat works

Simvastat is a prodrug in which the 6-membered lactone ring of simvastatin is hydrolyzed in vivo to generate the beta,delta-dihydroxy acid, an active metabolite structurally similar to HMG-CoA (hydroxymethylglutaryl CoA). Once hydrolyzed, simvastatin competes with HMG-CoA for HMG-CoA reductase, a hepatic microsomal enzyme, which catalyzes the conversion of HMG-CoA to mevalonate, an early rate-limiting step in cholesterol biosynthesis. Simvastat acts primarily in the liver, where decreased hepatic cholesterol concentrations stimulate the upregulation of hepatic low density lipoprotein (LDL) receptors which increases hepatic uptake of LDL. Simvastat also inhibits hepatic synthesis of very low density lipoprotein (VLDL). The overall effect is a decrease in plasma LDL and VLDL.

At therapeutic doses, the HMG-CoA enzyme is not completely blocked by simvastatin activity, thereby allowing biologically necessary amounts of mevalonate to remain available. As mevalonate is an early step in the biosynthetic pathway for cholesterol, therapy with simvastatin would also not be expected to cause any accumulation of potentially toxic sterols. In addition, HMG-CoA is metabolized readily back to acetyl-CoA, which participates in many biosynthetic processes in the body.

In vitro and in vivo animal studies also demonstrate that simvastatin exerts vasculoprotective effects independent of its lipid-lowering properties, also known as the pleiotropic effects of statins. This includes improvement in endothelial function, enhanced stability of atherosclerotic plaques, reduced oxidative stress and inflammation, and inhibition of the thrombogenic response.

Statins have also been found to bind allosterically to β2 integrin function-associated antigen-1 (LFA-1), which plays an important role in leukocyte trafficking and in T cell activation.

Dosage

Simvastat dosage

The patient should be placed on a standard cholesterol lowering diet before receiving Simvastat and should continue on this during treatment with Simvastat. The usual starting dose is 10 mg/day given as a single dose in the evening. Adjustment of dosage, if required, should be made at intervals of not less than four weeks, to a maximum of 40 mg daily given as a single dose in the evening. If LDL-cholesterol levels fall below 2 mmol/L or total plasma cholesterol levels fall below 3.5 mmol/L consideration should be given to reducing the dose of Simvastat. In hypercholesterolemia, the recommended starting dose is 5-10 mg once a day in the evening and the recommended dosing range is 5-40 mg per day as a single dose in the evening. In patients with coronary heart disease and hypercholesterolemia, the starting dose should be 20 mg once a day in the evening. Because Simvastat does not undergo significant renal excretion, modification of dosage should not be necessary in patients with renal insufficiency. Safety and effectiveness in children and adolescents have not been established.

Side Effects

Simvastat is generally well tolerated. Headache, fatigue, insomnia, gastrointestinal effects like nausea, constipation or diarrhoea, flatulence, dyspepsia, abdominal cramps and muscular effects like myalgia, myositis and myopathy have been reported. Rare cases of rhabdomyolysis with acute renal failure secondary to myoglobinuria have been associated with Simvastat therapy. Hepatitis, pancreatitis, rash, Angio-oedema have also been reported. No potentially life threatening effects have been reported.

Precaution

• If there is a history of liver disease
• Who take high alcohol
• Liver function test should be done before and during treatment
• If serum transaminase rises three times the upper limit of normal, treatment should be discontinued
• Avoid pregnancy during and for one month after treatment

Interaction

Digoxin: Concomitant administration of Simvastat and Digoxin in normal volunteers resulted in a slight elevation (less than 0.3 µgm/ml) in drug concentrations in plasma compared to concomitant administration of placebo and Digoxin.

Coumarin derivatives: Slightly enhance the anticoagulant effect of Warfarin (mean changes in p rothrombin time less than two seconds) in normal volunteers maintained in a state of low therapeutic anticoagulation.

Others: In clinical studies, Simvastat was used concomitantly with ACE inhibitors, beta-blockers, calcium channel blockers, diuretics and NSAIDs without evidence of clinically significant adverse interactions.

Food Interaction

• Avoid grapefruit products. Co-administration with grapefruit products may increase the risk for adverse effects such as myalgia.

[Major] GENERALLY AVOID: Coadministration with grapefruit juice may significantly increase the plasma concentrations of lovastatin and simvastatin and their active acid metabolites.

The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

When a single 60 mg dose of simvastatin was coadministered with 200 mL of double-strength grapefruit juice three times a day, simvastatin systemic exposure (AUC) increased by 16-fold and simvastatin acid AUC increased by 7-fold.

Administration of a single 20 mg dose of simvastatin with 8 ounces of single-strength grapefruit juice increased the AUC of simvastatin and simvastatin acid by 1.9-fold and 1.3-fold, respectively.

The interaction has also been reported with lovastatin, which has a similar metabolic profile to simvastatin.

Clinically, high levels of HMG-CoA reductase inhibitory activity in plasma is associated with an increased risk of musculoskeletal toxicity.

Myopathy manifested as muscle pain and

Rhabdomyolysis has also occurred rarely, which may be accompanied by acute renal failure secondary to myoglobinuria and may result in death.

ADJUST DOSING INTERVAL: Fibres such as oat bran and pectin may diminish the pharmacologic effects of HMG-CoA reductase inhibitors by interfering with their absorption from the gastrointestinal tract.

Coadministration with green tea may increase the plasma concentrations of simvastatin.

The mechanism of interaction has not been established, but may involve inhibition of organic anion transporting polypeptide (OATP) 1B1- and

The interaction was suspected in a 61-year-old man who experienced muscle intolerance during treatment with simvastatin while drinking an average of 3 cups of green tea daily.

He also experienced similar muscle intolerance (leg cramps without creatine phosphokinase elevation) during treatments with atorvastatin and rosuvastatin while drinking green tea.

Pharmacokinetic studies performed during his usual green tea intake demonstrated an approximately two-fold higher exposure to simvastatin lactone (the administered form of simvastatin) than that observed after stopping green tea intake for a month.

He was also able to tolerate simvastatin after discontinuing green tea consumption.

The authors of the report subsequently conducted two independent studies to assess the effect of different green tea preparations on simvastatin pharmacokinetics.

One study was conducted in 12 Italian subjects and the other in 12 Japanese subjects.

In the Italian study, administration of a single 20 mg dose of simvastatin following pretreatment with 200 mL of a hot green tea standardized infusion 3 times daily for 14 days (estimated daily intake of 335 mg total catechins and 173 mg epigallocatechin-3-gallate (EGCG), the most abundant and biologically active catechin in green tea) was found to have no significant effect on mean peak plasma concentration (Cmax) or systemic exposure (AUC) of simvastatin lactone and simvastatin acid relative to administration with water.

However, green tea increased simvastatin lactone AUC (0-6h) by about two-fold in 3 of the study subjects.

In the Japanese study, administration of a single 10 mg dose of simvastatin following pretreatment with 350 mL of a commercial green tea beverage twice daily for 14 days (estimated daily intake of 638 mg total catechins and 322 mg EGCG) did not affect mean simvastatin lactone Cmax or AUC to a statistically significant extent compared to administration with water, but increased mean simvastatin acid Cmax and AUC by 42% and 22%, respectively.

Similar to the first study, green tea increased simvastatin lactone AUC (0-6h) by two- to three-fold in 4 of the study subjects.

Although not studied, the interaction may also occur with lovastatin due to its similar metabolic profile to simvastatin.

MANAGEMENT: Patients receiving therapy with lovastatin, simvastatin, or red yeast rice (which contains lovastatin) should be advised to avoid the consumption of grapefruit and grapefruit juice.

Fluvastatin, pravastatin, pitavastatin, and rosuvastatin are metabolized by other enzymes and may be preferable alternatives in some individuals.

All patients receiving statin therapy should be advised to promptly report any unexplained muscle pain, tenderness or weakness, particularly if accompanied by fever, malaise and

Therapy should be discontinued if creatine kinase is markedly elevated in the absence of strenuous exercise or if myopathy is otherwise suspected or diagnosed.

Also, patients should either refrain from the use of oat bran and pectin, or separate the administration times by at least 2 to 4 hours if concurrent use cannot be avoided.

Caution may be advisable when coadministered with green tea or green tea extracts.

Dosing reduction of the statin and

Simvastat Alcohol interaction

[Moderate]

Concomitant use of statin medication with substantial quantities of alcohol may increase the risk of hepatic injury.

Transient increases in serum transaminases have been reported with statin use and while these increases generally resolve or improve with continued therapy or a brief interruption in therapy, there have been rare postmarketing reports of fatal and non-fatal hepatic failure in patients taking statins.

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

Active liver disease or unexplained transaminase elevations are contraindications to statin use.

Patients should be counseled to avoid substantial quantities of alcohol in combination with statin medications and clinicians should be aware of the increased risk for hepatotoxicity in these patients.

Simvastat Drug Interaction

Moderate: esomeprazoleMinor: levothyroxineUnknown: fluticasone / salmeterol, aspirin, aspirin, calcium / vitamin d, ubiquinone, duloxetine, omega-3 polyunsaturated fatty acids, insulin glargine, furosemide, pregabalin, metoprolol, metoprolol, clopidogrel, acetaminophen, cyanocobalamin, ascorbic acid, cholecalciferol, alprazolam

Simvastat Disease Interaction

Major: liver disease, rhabdomyolysis, renal dysfunctionModerate: cognitive impairment, diabetes, renal disease

Volume of Distribution

Rat studies indicate that when radiolabeled simvastatin was administered, simvastatin-derived radioactivity crossed the blood-brain barrier.

Elimination Route

Peak plasma concentrations of both active and total inhibitors were attained within 1.3 to 2.4 hours post-dose. While the recommended therapeutic dose range is 10 to 40 mg/day, there was no substantial deviation from linearity of AUC with an increase in dose to as high as 120 mg. Relative to the fasting state, the plasma profile of inhibitors was not affected when simvastatin was administered immediately before a test meal.

In a pharmacokinetic study of 17 healthy Chinese volunteers, the major PK parameters were as follows: Tmax 1.44 hours, Cmax 9.83 ug/L, t1/2 4.85 hours, and AUC 40.32ug·h/L.

Simvastat undergoes extensive first-pass extraction in the liver, the target organ for the inhibition of HMG-CoA reductase and the primary site of action. This tissue selectivity (and consequent low systemic exposure) of orally administered simvastatin has been shown to be far greater than that observed when the drug is administered as the enzymatically active form, i.e. as the open hydroxyacid.

In animal studies, after oral dosing, simvastatin achieved substantially higher concentrations in the liver than in non-target tissues. However, because simvastatin undergoes extensive first-pass metabolism, the bioavailability of the drug in the systemic system is low. In a single-dose study in nine healthy subjects, it was estimated that less than 5% of an oral dose of simvastatin reached the general circulation in the form of active inhibitors.

Genetic differences in the OATP1B1 (Organic-Anion-Transporting Polypeptide 1B1) hepatic transporter encoded by the SCLCO1B1 gene (Solute Carrier Organic Anion Transporter family member 1B1) have been shown to impact simvastatin pharmacokinetics. Evidence from pharmacogenetic studies of the c.521T>C single nucleotide polymorphism (SNP) showed that simvastatin plasma concentrations were increased on average 3.2-fold for individuals homozygous for 521CC compared to homozygous 521TT individuals. The 521CC genotype is also associated with a marked increase in the risk of developing myopathy, likely secondary to increased systemic exposure. Other statin drugs impacted by this polymorphism include rosuvastatin, pitavastatin, atorvastatin, lovastatin, and pravastatin.

For patients known to have the above-mentioned c.521CC OATP1B1 genotype, a maximum daily dose of 20mg of simvastatin is recommended to avoid adverse effects from the increased exposure to the drug, such as muscle pain and risk of rhabdomyolysis.

Evidence has also been obtained with other statins such as rosuvastatin that concurrent use of statins and inhibitors of Breast Cancer Resistance Protein (BCRP) such as elbasvir and grazoprevir increased the plasma concentration of these statins. Further evidence is needed, however a dose adjustment of simvastatin may be necessary. Other statin drugs impacted by this polymorphism include fluvastatin and atorvastatin.

Half Life

4.85 hours

Elimination Route

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

Pregnancy & Breastfeeding use

Category X: Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Contraindication

Simvastat should not be used in-

• Active liver disease
• Pregnant and breast feeding mother
• Women of child bearing age unless they have been adequately protected by contraception
• Hypersensitivity to any component of the preparation
• Patients with the homozygous familial hypercholesterolemia who have a complete absence of LDL receptors

Acute Overdose

There are no data available on overdose. No antidote is available. General measures should be adopted and liver function should be monitored.

Storage Condition

Store in a cool, dry place, Away from light keep out of reach of children.

Innovators Monograph

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