ATOZET TABLET 10MG/20MG

Ezetimibe
Atorvastatin

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

Ezedoc | Ezetimiba | Ezetimibum | Ezetrol | Ezetimibe |

Description

Ezetimibe is a lipid-lowering compound that inhibits intestinal cholesterol and related phytosterol absorption. The discovery and research of this drug began in the early 1990's, where intravenous administration of radio-labelled compound in rats resulting in subsequent localization of the drug within enterocytes at the intestinal villus, leading to studies of investigating the effect of ezetimibe on intestinal cholesterol absorption [A15202]. Ezetimibe is used as an adjunctive therapy to diet to lower cholesterol levels in primary hyperlipidemia, mixed hyperlipidemia, homozygous familial hypercholesterolemia (HoFH), and homozygous sitosterolemia (phytosterolemia) [FDA Label]. Unlike other classes of cholesterol-reducing compounds including statins and bile acid sequestrants, ezetimibe has a distinct mechanism of action involving the sterol transporter Niemann-Pick C1-Like 1 (NPC1L1), and is the first drug that does not affect absorption of fat-soluble nutrients such as fat-soluble vitamins, triglycerides, or bile acids [A33313]. In genetically NPC1L1-deficient mice, a 70% reduction in intestinal cholesterol absorption was seen and the mice were insensitive to ezetimibe treatment [A15202]. Based on these findings, it is indicated that NPC1L1 plays an essential role in promoting intestinal cholesterol uptake via an ezetimibe-sensitive pathway [A15202]. By interfering with the intestinal uptake of cholesterol and phytosterols, ezetimibe reduces the delivery of intestinal cholesterol to the liver [FDA Label].

Indication

Ezetimibe is indicated to reduce elevated total-C, LDL-C, Apo B, and non-HDL-C in patients with primary hyperlipidemia, alone or in combination with an HMG-CoA reductase inhibitor (statin), reduce elevated total-C, LDL-C, Apo B, and non-HDL-C in patients with mixed hyperlipidemia in combination with fenofibrate, reduce elevated total-C and LDL-C in patients with homozygous familial hypercholesterolemia (HoFH), in combination with atorvastatin or simvastatin, and to reduce elevated sitosterol and campesterol in patients with homozygous sitosterolemia (phytosterolemia) [FDA Label].

Mechanism of Action

Ezetimibe mediates its blood cholesterol-lowering effect via selectively inhibiting the absorption of cholesterol and phytosterol by the small intestine without altering the absorption of fat-soluble vitamins and nutrients [A15202]. The primary target of ezetimibe is the cholesterol transport protein Niemann-Pick C1-Like 1 (NPC1L1) protein. NPC1L1 is expressed at the enterocyte/ gut lumen (apical) as well as the hepatobiliary (canalicular) interface and plays a role in facilitating internalization of free cholesterol into the enterocyte in conjunction with the adaptor protein 2 (AP2) complex and clathrin [A33309]. Once cholesterol in the gut lumen or bile is incorporated into the cell membrane of enterocytes, it can bind to the sterol-sensing domain of NPC1L1 and form a NPC1L1/cholesterol complex. The complex can then be internalized or endocytosed by joining to AP2 clathrin, forming a vesicle complex that is translocated for storage in the endocytic recycling compartment [A33309]. Ezetimibe does not require exocrine pancreatic function for its pharmacological activity; rather, it localizes and appears to act at the brush border of the small intestine. Ezetimibe selectively blocks the NPC1L1 protein in the jejunal brush border, reducing the uptake of intestinal lumen micelles into the enterocyte [A33309]. Overall, ezetimibe causes a decrease in the delivery of intestinal cholesterol to the liver and reduction of hepatic cholesterol stores and an increase in clearance of cholesterol from the blood. While the full mechanism of action of ezetimibe in reducing the entry of cholesterol into both enterocytes and hepatocytes is not fully understood, a study proposed that ezetimibe prevents the NPC1L1/sterol complex from interacting with AP2 in clathrin coated vesicles and induces a conformational change in NPC1L1, rendering it incapable of binding to sterols [A33309]. Another study suggested that ezetimibe disrupts the function of other proteins complexes involved in regulating cholesterol uptake, including the CAV1– annexin 2 heterocomplex [A33309].

Pharmacodynamics

Ezetimibe was shown to reduce the levels of total cholesterol (total-C), low-density lipoprotein cholesterol (LDL-C), apoprotein B (Apo B), non-high-density lipoprotein cholesterol (non-HDL-C), and triglycerides (TG), and increase high-density lipoprotein cholesterol (HDL-C) in patients with hyperlipidemia [FDA Label]. This therapeutic effect was more profound when ezetimibe was co-administered with a statin or fenofibrate compared to either treatment alone [FDA Label]. In clinical trials involving patients with homozygous and heterozygous familial hypercholesterolemia and in those with sitosterolemia, a recommended therapeutic dose of ezetimibe was effective in reducing the LDL levels by 15-20% while increasing HDL-C by 2.5-5% [A33313].

Pharmacokinetics

Absorption:

Administration of a single 10-mg dose of ezetimibe in fasted adults resulted in a peak plasma concentrations (Cmax) of 3.4 to 5.5 ng/mL were achieved within 4 to 12 hours (Tmax) [FDA Label]. The Cmax of the major pharmacologically-active metabolite, ezetimibe-glucuronide, was 45 to 71 ng/mL and the Tmax was between 1 and 2 hours [FDA Label]. Food consumption had minimal effect on ezetimibe absorption, but the Cmax was increased by 38% with consumption of high-fat meals [FDA Label]. The absolute bioavailability of ezetimibe cannot be determined, as the compound is virtually insoluble in aqueous media suitable for injection [FDA Label].

Distribution:

The relative volume of distribution of ezetimibe is 107.5L [F133].

Metabolism:

In humans, ezetimibe is rapidly and extensively metabolized via a phase II glucuronide conjugation reaction in the small intestine and liver to form its main phenolic metabolite, ezetimibe glucuronide. The main human liver and/or intestinal uridine 5′-diphosphate (UDP)-glucuronosyltransferase (UGT) enzymes responsible for glucuronidating ezetimibe were shown to be UGT1A1, 1A3 and 2B15 _in vitro_ [A15202]. Minimal phase I reaction involving oxidation of ezetimibe also occurs to form SCH 57871, and human jejunum microsomes also produced trace levels of a benzylic glucuronide (SCH 488128) [A15202]. Ezetimibe glucuronide accounts for 80-90% of the total circulating compound in plasma, and retains some pharmacological activity in inhibiting intestinal cholesterol uptake [FDA Label]. In humans, ezetimibe and ezetimibe-glucuronide constitutes approximately 93% of the total drug in plasma [FDA Label]. Plasma concentration-time profiles exhibit multiple peaks, suggesting enterohepatic recycling [FDA Label], and about 20% of the drug distributed is reabsorbed due to enterohepatic re-circulation [F133].

Elimination:

Following oral administration, about 78% and 11% of the administered radio-labelled ezetimibe were recovered in the feces and urine, respectively [FDA Label]. Ezetimibe was the major component in feces and accounted for 69% of the administered dose as unconjugated compound, while ezetimibe-glucuronide was the major component in urine and accounted for 9% of the administered dose [FDA Label]. High recovery of unchanged parent drug in feces suggests low absorption and/or hydrolysis of ezetimibe-glucuronide secreted in the bile [A15202].

Half-life

Both ezetimibe and ezetimibe-glucuronide display an approximate half-life of 22 hours [FDA Label].

Clearance

There is no pharmacokinetic data available on the clearance of ezetimibe.

Toxicity

Oral LD50 and intraperitoneal LD50 in rat were >2000 mg/kg [MSDS]. Estimated oral LD50 values in mouse and dog are >5000 mg/kg and >3000 mg/kg, respectively [MSDS]. One case of accidental overdose occurred in clinical studies in one female patient with homozygous sitosterolemia receiving 120 mg/day for 28 days with no reported clinical or laboratory adverse events [FDA Label]. In case of overdose, symptomatic treatment is recommended [FDA Label].

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

atorvastatina | atorvastatine | atorvastatinum | Atorvastatin |

Description

Atorvastatin (Lipitor) is a member of the drug class known as statins. It is used for lowering cholesterol. Atorvastatin is a competitive inhibitor of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-determining enzyme in cholesterol biosynthesis via the mevalonate pathway. HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate. Atorvastatin acts primarily in the liver. Decreased hepatic cholesterol levels increases hepatic uptake of cholesterol and reduces plasma cholesterol levels.

Indication

May be used as primary prevention in individuals with multiple risk factors for coronary heart disease (CHD) and as secondary prevention in individuals with CHD to reduce the risk of myocardial infarction (MI), stroke, angina, and revascularization procedures. May be used to reduce the risk of cardiovascular events in patients with acute coronary syndrome (ACS). May be used in the treatment of primary hypercholesterolemia and mixed dyslipidemia, homozygous familial hypercholesterolemia, primary dysbetalipoproteinemia, and/or hypertriglyeridemia as an adjunct to dietary therapy to decrease serum total and low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apoB), and triglyceride concentrations, while increasing high-density lipoprotein cholesterol (HDL-C) levels.

Mechanism of Action

Atorvastatin selectively and competitively inhibits the hepatic enzyme HMG-CoA reductase. As HMG-CoA reductase is responsible for converting HMG-CoA to mevalonate in the cholesterol biosynthesis pathway, this results in a subsequent decrease in hepatic cholesterol levels. Decreased hepatic cholesterol levels stimulates upregulation of hepatic LDL-C receptors which increases hepatic uptake of LDL-C and reduces serum LDL-C concentrations.

Pharmacodynamics

Atorvastatin, a selective, competitive HMG-CoA reductase inhibitor, is used to lower serum total and LDL cholesterol, apoB, and triglyceride levels while increasing HDL cholesterol. High LDL-C, low HDL-C and high TG concentrations in the plasma are associated with increased risk of atherosclerosis and cardiovascular disease. The total cholesterol to HDL-C ratio is a strong predictor of coronary artery disease and high ratios are associated with higher risk of disease. Increased levels of HDL-C are associated with lower cardiovascular risk. By decreasing LDL-C and TG and increasing HDL-C, atorvastatin reduces the risk of cardiovascular morbidity and mortality. Atorvastatin has a unique structure, long half-life, and hepatic selectivity, explaining its greater LDL-lowering potency compared to other HMG-CoA reductase inhibitors.

Pharmacokinetics

Absorption:

Atorvastatin is rapidly absorbed after oral administration with maximum plasma concentrations achieved in 1 to 2 hours. The absolute bioavailability of atorvastatin (parent drug) is approximately 14% and the systemic availability of HMG-CoA reductase inhibitory activity is approximately 30%. The low systemic bioavailability is due to presystemic clearance by gastrointestinal mucosa and first-pass metabolism in the liver.

Distribution:

381 L

Metabolism:

Atorvastatin is extensively metabolized to ortho- and parahydroxylated derivatives and various beta-oxidation products. In vitro inhibition of HMG-CoA reductase by ortho- and parahydroxylated metabolites is equivalent to that of atorvastatin. Approximately 70% of circulating inhibitory activity for HMG-CoA reductase is attributed to active metabolites. CYP3A4 is also involved in the metabolism of atorvastatin.

Elimination:

Eliminated primarily in bile after hepatic and/or extrahepatic metabolism. Does not appear to undergo significant enterohepatic recirculation. Less than 2% of the orally administered dose is recovered in urine.

Half-life

14 hours, but half-life of HMG-CoA inhibitor activity is 20-30 hours due to longer-lived active metabolites

Clearance

Not Available

Toxicity

Generally well-tolerated. Side effects may include myalgia, constipation, asthenia, abdominal pain, and nausea. Other possible side effects include myotoxicity (myopathy, myositis, rhabdomyolysis) and hepatotoxicity. To avoid toxicity in Asian patients, lower doses should be considered.

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

ATOZET TABLET 10MG/20MG was registered with Health Science Authority of Singapore by MSD PHARMA (SINGAPORE) PTE LTD. It is marketed with the registration number of SIN15114P with effective from 2016-11-09.

This product contains 10mg of Ezetimibe, and 20mg of Atorvastatin in the form of ORAL TABLET, FILM-COATED.

The medicine was manufactured by MSD INTERNATIONAL GMBH in SINGAPORE, and MSD International GmbH (Puerto Rico Branch) LLC in PUERTO RICO

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

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