DESCRIPTION
Atorvastatin-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. Ezetimibe-Ezetimibe is an anti-hyperlipidemic medication which is used to lower cholesterol levels. Specifically, it appears to bind to a critical mediator of cholesterol absorption, the Niemann-Pick C1-Like 1 (NPC1L1) protein on the gastrointestinal tract epithelial cells as well as in hepatocytes.
CATEGORIES
Atorvastatin-Anticholesteremic Agents,Hydroxymethylglutaryl-CoA Reductase Inhibitors. Ezetimibe-Cholesterol Absorption Inhibitors.
CHEMICAL FORMULA
Atorvastatin-C33H34FN2O5.Ezetimibe-C24H21F2NO3.
COMPOSITION
Atorvastatin 10mg + Ezetimibe 10mg
INDICATION
Atorvastatin-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. Ezetimibe-For use as adjunctive therapy to diet for the reduction of elevated total-C, LDL-C, and Apo B in patients with primary (heterozygous familial and non-familial) hypercholesterolemia.
PHARMACODYNAMICS
Atorvastatin-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. Ezetimibe-Ezetimibe is in a class of lipid-lowering compounds that selectively inhibits the intestinal absorption of cholesterol and related phytosterols. Ezetimibe, administered alone is indicated as adjunctive therapy to diet for the reduction of elevated total-C, LDL-C, and Apo B in patients with primary (heterozygous familial and non-familial) hypercholesterolemia. It is also used in combination therapy with HMG-CoA reductase inhibitors. Ezetimibe has a
MECHANISM
of action that differs from those of other classes of cholesterol-reducing compounds (HMG-CoA reductase inhibitors, bile acid sequestrants, fibric acid derivatives, and plant stanols). Ezetimibe does not inhibit cholesterol synthesis in the liver, or increase bile acid excretion but instead localizes and appears to act at the brush border of the small intestine and inhibits the absorption of cholesterol, leading to a decrease in the delivery of intestinal cholesterol to the liver. This causes a reduction of hepatic cholesterol stores and an increase in clearance of cholesterol from the blood; this distinct
MECHANISM
is complementary to that of HMG-CoA reductase inhibitors.
MECHANISM
Atorvastatin-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. Ezetimibe-Ezetimibe localizes and appears to act at the brush border of the small intestine and inhibits the absorption of cholesterol. This leads to a decrease in the delivery of intestinal cholesterol to the liver.
ABSORPTION
Atorvastatin-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. Ezetimibe-After oral administration, ezetimibe is absorbed and extensively conjugated to a pharmacologically active phenolic glucuronide (ezetimibe-glucuronide). When a single 10 mg dose of ezetimibe is given to a fasted, male, adult subject, the pharmacokinetic parameters are as follows: Cmax = 3.5 – 5.5 ng/mL; Tmax = 4- 12 hours. The pharmacokinetic parameters for ezetimibe-glucuronide are as follows: Cmax = 45 – 71 ng/mL; Tmax = 1-2 hours. Food has not impact on the extent of absorption of ezetimibe. However, Cmax increases by 38% with a high-fat meal.
VOLUME DISTRIBUTION
Atorvastatin-381 L.
METABOLISM
Atorvastatin-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. Ezetimibe-Ezetimibe is primarily metabolized in the small intestine and liver via glucuronide conjugation (a phase II reaction) with subsequent biliary and renal excretion. In humans, ezetimibe is rapidly metabolized to ezetimibe-glucuronide.
ELIMINATION
Atorvastatin-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. Ezetimibe-78% of the dose is excreted into feces. 11% of the dose is excreted into urine. Ezetimibe was the major component in feces and accounted for 69% of the administered dose, while ezetimibe-glucuronide was the major component in urine and accounted for 9% of the administered dose.
HALF LIFE
Atorvastatin-14 hours, but half-life of HMG-CoA inhibitor activity is 20-30 hours due to longer-lived active metabolites. Ezetimibe-22 hours (both ezetimibe and ezetimibe-glucuronide).
TOXICITY
Atorvastatin-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. Ezetimibe-The most common adverse reactions in the group of patients treated with ezetimibe that led to treatment discontinuation and occurred at a rate greater than placebo were, arthralgia (0.3%), dizziness (0.2%), and gamma-glutamyltransferase increase (0.2%).
FOOD INTERACTIONS
avoid alcohol.
SIDE EFFECTS
Atorvastatin-Headache, Belly pain, Loose stools (diarrhea), Muscle weakness, Joint pain. Ezetimibe-Feeling dizzy. Rise slowly over a few minutes when sitting or lying down. Be careful climbing. Headache. Belly pain. Joint pain. Loose stools (diarrhea). Feeling tired or weak. Runny nose. Sore throat.