Dosing of Zocor vs. Lipitor

Summary: The dosing of Zocor vs. Lipitor isn’t equal on a milligram per milligram basis. If you make the switch from Zocor to Lipitor you’ll likely find that your doctor is forced to cut the strength in half as well.

Dear Curtis: I was on Simvastatin 80mg a day until my doctor said they are recalling it. He switched me to Lipitor 40mg a day. I didn’t catch it at first but it’s only half the strength of my Zocor. Is this going to do anything? Should I call my doctor and let him know he made a mistake?

First, Zocor 80 mg wasn’t recalled.

A recall means the drug has been pulled from the market and is no longer available. Zocor (simvastatin) 80 mg is still being used by some patients, especially folks who have been on it a year or more with no signs of any sort of muscle pain.

Dosing Differences Between Lipitor and Zocor

It’s a pretty common misconception that when you switch to another drug in the same class that does the same thing as what you were taking – that the dose should remain the same.

But it actually doesn’t work that way.

Once upon a time I worked in a mail order pharmacy where one of my jobs was to switch people between these medications. Everyday I saw that when we made the switch the dose of Lipitor needed was almost always half the dose of Zocor.

So it’s not a straight across the board switch.

For example, Lipitor 10 mg a day will generally produce about a 25% to 37% drop in total cholesterol. Zocor, at 10 mg a day, produced a 23% drop in total cholesterol. At 20 mg a day of Zocor particpants saw their total cholesterol drop by 28%.

The same story held true for lowering of LDL cholesterol. At 10 mg of Lipitor a day LDL dropped 27% to 39%. With Zocor 10 mg a day LDL dropped by 30%.

Lipitor “Better” Than Zocor?

So, does this mean Zocor is a ‘better’ cholesterol lowering drug than Lipitor?

Not always. For example, before this news came up about Zocor’s drug interactions and the increased risk of muscle pains the generic Zocor (simvastatin) was very popular because it was cheaper. The fact remains it’s still popular because of it’s price.

I’d also like to point out that while simvastatin has received a lot of bad press lately, all the drugs in this class can cause side effects like muscle pain.

Also, some folks don’t tolerate Lipitor as well so they prefer other agents.

But, the fact remains, your doctor didn’t actually make a mistake. When he switched you from Zocor to Lipitor it was correct to lower the dose.

References:

  1. Lipitor [package insert]. New York, NY: Parke-Davis; February 2009.
  2. Zocor [package insert]. Whitehouse Station, NJ: Merck & Co Inc; June 2011.