Are there differences among statins?

Statins differ in several ways. The most obvious difference is in their ability to reduce cholesterol. Currently, atorvastatin (Lipitor) and rosuvastatin (Crestor) are the most potent, and fluvastatin (Lescol) is the least potent.

The statins also differ in how strongly they interact with other drugs. Specifically, pravastatin (Pravachol) and rosuvastatin (Crestor) levels in the body are less likely to be elevated by other drugs that may be taken at the same time as the statins. This is so because the enzymes in the liver that eliminate pravastatin and rosuvastatin are not blocked by many of the drugs that block the enzymes that eliminate other statins. This prevents the levels of pravastatin and rosuvastatin from rising and leading to increased toxicity such as myopathy (inflammation of the muscles). For example, in scientific studies, patients who took both verapamil (Calan, Verelan, Verelan PM, Isoptin, Isoptin SR, Covera-HS) and simvastatin (Zocor) experienced myopathy 10 times more often than patients who received simvastatin alone because verapamil increased the blood levels of simvastatin.

Statins differ in the frequency with which they cause a severe type of myopathy called rhabdomyolysis, in which muscles are severely damaged. Cerivastatin (Baycol) was withdrawn from pharmacies worldwide because it caused rhabdomyolysis 10 to 100 times more often than other statins. Rhabdomyolysis may occur more often in patients taking statins with drugs that also cause rhabdomyolysis or drugs that increase the blood concentration of the statin.

What are the side effects of statins?

The most common side effects are:

• headache,
  
  
• nausea,
  
  
• vomiting,
  
  
• constipation,
  
  
• diarrhea,
  
  
• rash,
  
  
• weakness, and
  
  
• muscle pain.

The most serious (but fortunately rare) side effects are liver failure and rhabdomyolysis. Rhabdomyolysis is a serious side effect in which there is damage to muscles. Rhabdomyolysis often begins as muscle pain and can progress to loss of muscle cells, kidney failure, and death. It occurs more often when statins are used in combination with other drugs that themselves cause rhabdomyolysis or with drugs that prevent the elimination of statins and raise the levels of statins in the blood. Since rhabdomyolysis may be fatal, unexplained joint or muscle pain that occurs while taking statins should be brought to the attention of a healthcare provider for evaluation. Statins must not be used during pregnancy because of the risk of serious adverse effects to the developing fetus.

With which drugs do statins interact?

Statins have some important drug interactions. The first type of interaction involves the enzymes responsible for the elimination of statins by the liver. Liver enzymes (specifically, the cytochrome P-450 liver enzymes) are responsible for eliminating all statins from the body with the exception of pravastatin and rosuvastatin. Therefore, drugs that block the action of these liver enzymes increase the levels of simvastatin, lovastatin, fluvastatin, and atorvastatin (but not pravastatin or rosuvastatin) in the blood and can lead to the development of rhabdomyolysis. Drugs or agents that block these enzymes include:

• protease inhibitors (used in treating AIDS),
  
  
• erythromycin,
  
  
• itraconazole, (Sporanox)
  
  
• clarithromycin, (Biaxin)
  
  
• diltiazem, (Cardizem, Dilacor, Tiazac)
  
  
• verapamli (Calan, Verelan, Verelan PM, Isoptin, Isoptin SR, Covera-HS), and
  
  
• grapefruit juice.

Another important drug interaction occurs between statins and niacin or fibric acids, for example, gemfibrozil (Lopid), clofibrate (Atromid-S), and fenofibrate (Tricor). Niacin and the fibric acid drugs can cause rhabdomyolysis or liver failure when used alone, and combining them with statins increases the likelihood of rhabdomyolysis or liver failure. Nevertheless, fibric acids and niacin are often used with caution in combination with most statins. Cholestyramine (Questran) as well as colestipol (Colestid) bind statins in the intestine and reduce their absorption into the body. To prevent this binding within the intestine, statins should be taken one hour before or four hours after cholestyramine or colestipol.

From the Doctors at MedicineNet.com

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