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Lipitor |
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Atorvastatin (INN), marketed under the trade name Lipitor and several others, is a member of the drug class known as statins, used for lowering cholesterol.
Atorvastatin inhibits the rate-determining enzyme located in hepatic
tissue that produces mevalonate, a small molecule used in the synthesis
of cholesterol and other mevalonate derivatives. This lowers the amount
of cholesterol produced which in turn lowers the total amount of LDL
cholesterol. With 2006 sales of US$12.9 billion under the brand name Lipitor, it is the largest selling drug in the world. Lipitor is not the only statin. There are over 5 other statins in the market. Pharmacology As with other statins, atorvastatin is a competitive inhibitor of HMG-CoA reductase. Unlike most others, however, it is a completely synthetic compound. HMG-CoA reductase catalyzes the reduction of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) to mevalonate, which is the rate-limiting step in hepatic cholesterol biosynthesis. Inhibition of the enzyme decreases de novo cholesterol synthesis, increasing expression of low-density lipoprotein receptors (LDL receptors) on hepatocytes. This increases LDL uptake by the hepatocytes, decreasing the amount of LDL-cholesterol in the blood. Like other statins, atorvastatin also reduces blood levels of triglycerides and slightly increases levels of HDL-cholesterol. In clinical trials, adding ezetimibe (Zetia) to Lipitor lowered cholesterol more effectively than Vytorin (ezetimibe + simvastatin). Clinical use Indications Atorvastatin is indicated as an adjunct to diet for the treatment of dyslipidemia, specifically hypercholesterolaemia. It has also been used in the treatment of combined hyperlipidemia. In 2005, the PROVE IT-TIMI 22 trial compared 40mg/day pravastatin with 80mg/day atorvastatin. Taken directly from the results of the trial: "Standard treatment (statin) with a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (pravastatin 40 mg/day) resulted in a 22% reduction in LDL cholesterol levels at 30 days compared with a 51% reduction with intensive therapy (atorvastatin 80 mg/day). At 2 years, a relative risk reduction of 16% (95% confidence interval, 5%-26%; P = 0.005) in the primary end point rate (death, myocardial infarction, documented unstable angina requiring hospitalization, coronary revascularization, or stroke) was seen in patients receiving intensive statin treatment compared with standard statin therapy. The benefit of intensive treatment was apparent as early as 30 days and was consistent over time. The PROVE IT-TIMI 22 data indicate that patients recently hospitalized for an ACS benefit from early and continued lowering of LDL cholesterol to levels substantially below current guideline recommendations." Available forms Atorvastatin calcium tablets are currently marketed by Pfizer under the trade name Lipitor, in tablets (10, 20, 40 or 80 mg) for oral administration. Tablets are white, elliptical, and film coated. In some countries it is also be sold under the trade names Sortis, Torvast, Torvacard, Totalip, Tulip, Xarator, Atorpic, Liprimar, and Atorlip. Pfizer also packages the drug in combination with other drugs, such as is the case with its Caduet. Adverse effects Common adverse drug reactions (≥1% of patients) associated with atorvastatin therapy include: myalgia, mild transient gastrointestinal symptoms (diarrhea, constipation, passing gas), elevated hepatic transaminase concentrations, headache, insomnia, joint pain, and/or dizziness. Myopathy and rhabdomyolysis occur in <0.1% of patients. Risk is increased in patients with renal impairment, serious concurrent illness; and/or concomitant use of drugs which inhibit CYP3A4. |
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