Lipitor
Lipitor
Lipitor [atorvastatin] is a lipid lowering agent marketed by PFIZER.
It is a synthetic compound of the statin group of drug which helps in lowering the cholesterol levels in the blood. [Lipid lowering agent]
With 2006 sales of US$12.9 billion under the brand name Lipitor, it is the largest selling drug in the world
Lipitor [atorvastatin] is a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A [HMG-CoA] reductase, which catalyzes an early, rate limiting step in cholesterol biosynthesis. Lipitor [atorvastatin] inhibits this rate-determining enzyme located in hepatic tissue that produces mevalonate, a small molecule used in the synthesis of cholesterol and other mevalonate derivatives. This increases LDL uptake by the liver cells, hepatocytes, decreasing the amount of LDL-cholesterol in the blood. Atorvastatin, a calcium salt is an entirely synthetic compound containing a hepatanoic acid chain that forms a structural analog of the HMG-CoA intermediate.
This leads us to think, why we need to have lower levels of cholesterol?
Well, in a nutshell, we have 4 types of lipoproteins in our body, namely,
- High density lipoproteins [HDL]
- Low density lipoproteins [LDL]
- Very low density lipoprotein [VLDL]
- Chylomicrons.
Of these, high density lipoproteins are the good lipoproteins while the rest are considered bad for the heart.
Cholesterol is a low density lipoprotein and hence needs to be kept in check, since it has been documented at great lengths that increased cholesterol leads to the formation of atherosclerosis which can aggravate myocardial injury in the form of myocardial ischemia further leading to myocardial infarction.
Hypercholesterolemia is the presence of high levels of cholesterol in the blood. It's not a disease but a metabolic derangement that can be secondary to many diseases and can contribute to many forms of disease, mainly diseases of the cardiovascular system.
Now, researchers say that even normal levels of cholesterol can be heart damaging leading to the term dyslipidemia.
Dyslipidemia is a disruption in the amount of lipids in the blood.
In western societies, most dyslipidemias are hyperlipidemias; that is, an elevation of lipids in the blood, often due to diet and lifestyle. The prolonged elevation of insulin levels can lead to dyslipidemia. Increased levels of O-GlcNAc transferase (OGT) are known to cause dyslipidemia.
Lipitor [atorvastatin] affects blood cholesterol level by inhibiting cholesterogenesis in the liver, which results in increased expression of LDL receptor gene. The greater number of LDL receptors on the surface of hepatocytes results in increased removal of LDL from the blood, thereby lowering LDL-C levels.
Thus, Lipitor [atorvastatin] is extensively used for Prevention of Cardiovascular Disease since it works in-
Reducing risk of myocardial infarction
Reducing risk of stroke
Reducing risk for angina and revascularization procedures
Lipitor [atorvastatin] is extensively metabolized by CYP3A4, an isoform of cytochrome P450.Lipitor has a long half life, which allows administration of this statin at any time of the day
Adverse Effects and Drug Interactions:
- Hepatotoxicity: Increased levels of hepatic transaminase to values greater than three times the upper limit of normal. Hence it is advisable to measure alanine aminotranferase [ALT] at baseline and 3 to 6 months after therapy is initiated or after increasing the dose. If the ALT values are normal, it is not necessary to repeat the ALT test more than 6 to 12 months. Special precaution must be taken while giving Lipitor [atorvastatin] to patients with history of liver disease.
- Myopathy: defined as muscle aches or muscle weakness in conjunction with increases in creatine phosphokinase (CPK) values >10 times ULN Atorvastatin therapy should be temporarily withheld or discontinued in any patient with an acute, serious condition suggestive of a myopathy or having a risk factor predisposing to the development of renal failure secondary to rhabdomyolysis (e.g., severe acute infection, hypotension, major surgery, trauma, severe metabolic, endocrine and electrolyte disorders, and uncontrolled seizures).
- reversible myositis
- Gastro-intestinal effects like: Abdominal pain, flatulence, nausea and vomiting
- Respiratory System: Bronchitis, rhinitis, pneumonia, dyspnea, asthma, epistaxis.
- Nervous System: Insomnia, dizziness, paresthesia, somnolence, amnesia, abnormal dreams, libido decreased, emotional lability, in coordination, peripheral neuropathy, torticollis, facial paralysis, hyperkinesia, depression, hypesthesia, hypertonia.
- Headache
- Altered Liver Function Tests [LFTs]
- Anorexia
- Alopecia
- Impotence
- Chest pain
- Hypoglycemia
- Hyperglycemia
Drug interactions:
- Antacids
- Colestipol
- Digoxin
- Erythromycin [Macrolide antibiotics]
- Oral contraceptive pills
- Fibric acid derivatives like clofibrate, fenofibrate, gemfibrozil
- Cyclosporine
- Niacin
- HIV or AIDS medication such as indinavir, nelfinavir, ritonavir, lopinavir-ritonavir, or saquinavir.
Special Precautions:
- History of liver disease
- Chronic alcoholism
- Unexplained muscle weakness and pain
- Pregnancy
- Children under 10 years of age. There are no studies documented on children less than 10 years
Therapeutic Uses:
- Primary hypercholesterolemia
- Heterozygous familial hypercholesterolemia
- Homozygous familial hypercholesterolemia
- Combined hyperlipidemias.
Dosage:
Lipitor [atorvastatin] is available in tablets of atorvastatin calcium containing 10, 20, 40 and 80 mg atorvastatin. It is started at 10 mg daily and may be increased to up to 80 mg/day
Lipitor [atorvastatin] and simvastatin have somewhat similar rates in decreasing cardiovascular morbidity and mortality. However the main clinical advantage of Lipitor over Simvastatin is that it is not metabolized by certain liver enzymes, thus its blood concentration is not increased when combined with grapefruit juice which inhibits these enzymes. That means that patients on simvastatin should refrain from drinking grapefruit juice.
Samir is the author of Lipitor, Atorvastatin information located at Genericsmed.com site
References:
- Pharmacology and Pharmacotherapeutics, R.S.Satoskar, S.D.Bhandarkar, S.S.Ainapure, Revised 17th Edition, pg 563-564
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 10th Edition, pgs 984-988
- Drug Today, July-September 2005 Edition, pg 834-836
- Harrison's Principles of Internal Medicine, 16th Edition, pg 2296
- http://en.wikipedia.org/wiki/Atorvastatin
- http://en.wikipedia.org/wiki/Hypercholesterolaemia
- http://en.wikipedia.org/wiki/Dyslipidemia
- http://www.rxlist.com/cgi/generic/atorvastatin.htm
- http://www.drugs.com/lipitor.html
- http://www.pdrhealth.com/drugs/rx/rx...&contentId=311
