Hello there from Dr. K, your War on Diabetes pharmacist. Today I’m going to start a new series of posts on cholesterol medications. For an overview of all of the types of cholesterol medications currently available, you can read my previous post here.

Doctors and the media are talking about it all the time, but where does cholesterol come from, and what is it?  In a very simplified explanation, cholesterol is a form of fat.  We get much of our cholesterol from the foods we eat – animal products such as meat, dairy products, butter, and eggs all contain cholesterol.  All of our bodies need some cholesterol for breaking down the food we eat, making Vitamin D and important hormones like estrogen and testosterone, and for making the external coating or membrane on the cells in the body.  But too much cholesterol can clog our blood vessels and cause heart disease, strokes, chest pain, heart attacks, and death.

The first question you may be asking is: I thought this was a diabetes blog, why are we talking about cholesterol?  What a great question!  In answer to that, cholesterol is very important to diabetics.  Diabetes is what we call a “risk factor” for the development of heart disease; if you have diabetes, you are more likely to have heart problems than if you did not have diabetes.  High cholesterol is another risk factor for heart disease, so you can see why you would not want to have more than one risk factor (diabetes and high cholesterol).  Diabetes and high cholesterol seem to go hand in hand with one another.  Many times high cholesterol levels can predict future diabetes – high levels of bad cholesterol tend to show up before a person is diagnosed with diabetes.  Higher levels of insulin in the blood (which happens when a person first gets type 2 diabetes, as their body tries to make more insulin to overcome the fact that the cells are no longer responding to insulin) tend to lead to high levels of bad cholesterol.

“But Dr. K, I have my blood sugars under control and am currently winning my War on Diabetes, what about me?”  First of all, that is fantastic!  However, even if your blood sugars are under control you are still at a greater risk of having high cholesterol simply because of the diabetes.  Diabetics, no matter how controlled their blood sugars are, have been found to have higher triglycerides and lower good cholesterol (HDL), as well as sometimes increased bad cholesterol (LDL).  And the type of diabetes that you have is important too – the type of cholesterol-caused plaques that form in the arteries of type 2 diabetics tend to be fattier and less fibrous than the plaques that form in type 1 diabetics.  What does that mean?  Well, these types of plaques are more likely to break away from where they are in the arteries and float into the bloodstream, leading to strokes and heart attacks.  For these reasons, the American Diabetes Association recommends checking cholesterol levels in diabetics yearly, and more often if cholesterol is high and not controlled by medication.

So as you can see, cholesterol medications are essential to people with diabetes.  We try to provide a comprehensive approach to our diabetes blog, so I’m going to be covering the most common medications used to control cholesterol.  I’m starting with the most popular class of medications and one of the most popular medications in that class.  Its brand name is Zocor, but we know it as simvastatin.

How does it lower cholesterol: Simvastatin is an HMG-CoA reductase inhibitor (more commonly known as a “statin”).  What in the world does that mean?  HMG-CoA reductase is an enzyme in the body that is essential for making cholesterol.  Simvastatin works by stopping this enzyme from working, which stops the body from making cholesterol.  Also, simvastatin helps to remove cholesterol from the body.

The effect on your numbers: The primary effect of simvastatin is on your bad cholesterol, or LDL.  With all of the statins, the amount of decrease on your cholesterol is related to the dose – the higher the dose the more you lower your cholesterol.  However, this effect plateaus after a certain dose.  This means that we can only increase simvastatin to a certain dose and after that point we see little benefit.  What do we see instead?  More side effects!  For this reason, the FDA has put guidelines that limit the maximum dose of simvastatin to 40 mg or less (unless you are on another medication that increases the effectiveness of simvastatin, which I will discuss in a bit).  If your cholesterol is not low enough at 40 mg, your doctor should consider switching you to another cholesterol medication.

So for a reference, I will tell you approximately how much each dose of simvastatin will lower your LDL:

Simvastatin 10 mg – lowers LDL by about 30%

Simvastatin 20 mg – lowers LDL by about 38%

Simvastatin 40 mg – lowers LDL by about 41%

Simvastatin 80 mg – lowers LDL by about 47%, but has many more side effects so should not be used, unless you have been on 80 mg of simvastatin for more than 12 months and have not shown any signs of muscle toxicity

Dosing: Dosing is based on a few things – how high your LDL is and how much it needs to be lowered (see the list above), side effects, and other medications you are on.  For example, if you are taking verapamil or diltiazem your dose of simvastatin should be no more than 10 mg daily.  You should not be on more than 20 mg of simvastatin if you are also taking amlodipine, amiodarone, or ranolazine.

Side effects: For the most part, side effects of simvastatin are generally mild and include abdominal pain (7.3% of patients), constipation (6.6%), nausea (5.4%), headache (up to 7.4%), and upper respiratory infection (9%).  The more major side effects that we normally hear about with simvastatin really are quite rare: liver injury or elevated liver enzyme levels (1% of patients), muscle disorders (0.03% of patients on 20mg/day, 0.08% on 40mg/day, and 0.9% on 80mg/day), and serious breakdown of muscle fibers known as rhabdomyolysis (0% of patients on 20mg/day, 0.4% of patients on 80mg/day).  These major side effects are more commonly found when patients are taking another drug with simvastatin that makes them more likely to develop side effects, which is why I will discuss those medications in a bit under drug interactions.

The FDA has put out a consumer update in regards to liver and muscle problems with statins, as well as addressing other safety issues that have been reported to them involving memory loss and increased blood sugars potentially caused by statins.  I will provide a link to this information for you, but will summarize the report very briefly.  There have been a small number of patients that have experienced “fuzzy or unfocused thinking,” which was not severe and stopped when the statin was stopped.  Also, a small risk of increased blood sugars and development of type 2 diabetes has been found for some people when placed on statins.  However, the FDA is quick to say that both of these instances are very rare and minor, and should not be used as reasons for discontinuing your statins.  Statins have been shown to be extremely beneficial in reducing the risk of heart disease, stroke, and death and the benefits of this far outweigh the potential risks of these rare side effects.  If you are at all concerned about these risks, do not stop taking your medication without talking with your local physician.

Who should not take simvastatin: If you have active liver disease you should not take simvastatin.  Also, if you are pregnant or nursing or may become pregnant you should not use simvastatin because it can cause harm to the baby.

There are also a list of other conditions and characteristics that can make you more susceptible to muscle damage/weakness or liver problems while on simvastatin, so you should talk to your doctor if you have any concerns.  Some of these instances include ALS, age greater than 65, female gender, Chinese descent patients also taking niacin, sepsis, hypotension, uncontrolled epilepsy, surgery or trauma, uncontrolled hypothyroidism, liver or kidney disease, and substantial use of alcohol.

Drug interactions: Earlier I talked about how patients on certain medications should be on lower doses of simvastatin.  Well, there is another list of medications that should not be used at all with simvastatin, because they can cause you to be at increased risk of the major side effects I just mentioned.  Those medications include:

  • Itraconazole
  • Ketoconazole
  • Posaconazole
  • Erythromycin
  • Clarithromycin
  • Telithromycin
  • Nefazodone
  • Gemfibrozil
  • Cyclosporine
  • Danazol
  • HIV protease inhibitors (atazanavir/Reyataz, darunavir/Prezista, fosamprenavir/Lexia, indinavir/Crixivan, nelfinavir/Viracept, ritonavir/Norvir, saquinavir/Invirase, tipranavir/Aptivus)

One more interesting fact of note: grapefruit and grapefruit juice can interfere with simvastatin in large quantities.  So if you are an avid fan of grapefruit juice, limit yourself to no more than one quart daily.

There are other medications that are known to interact with simvastatin.  If you have questions, please contact your local doctor or pharmacist.

If you would like to read more about simvastatin, here is another good website:

Stay tuned for my next post on another cholesterol medication in the statin family!

1 Comment on “Simvastatin

  1. Thank you for the grapefruit information. I discovered this the hard way. I was eating grapefruit and wondering why I was having so much muscle pain. My wife went to her medication guide and was able to see that eating or drinking grapefruit and some related products causes exactly the problem you displayed.

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