Wednesday, January 16, 2008

Zetia, Premarin, and the safety of medicines

Part of our Federal tax money goes to support the Food and Drug Administration (FDA), charged with overseeing the safety of medicines sold in America. The pharmaceutical companies are quick to describe how very expensive it is to take a proposed new medicine through the FDA approval process. So, why is the effectiveness and even safety of Zetia, (ezetimibe; a component of Vytorin) a cholesterol reducing medicine, being questioned now quite some time after its FDA approval.

Everyone would like their risks of heart attacks and strokes to be reduced. This is the ultimate goal of preventing and treating cardiovascular diseases, the number 1 cause of deaths in the US. Heart attacks and strokes are thought to be caused by cholesterol plaque being deposited in the walls of blood vessels thus narrowing them or by clots lodging in the blood vessels of the heart and brain.

The ideal means of experimenting with a proposed medicine for reducing the risks of heart attacks and strokes would be to treat some people with the medicine and not treat others. Then, wait to see which group gets more and which group gets fewer heart attacks and strokes. And, ideally, everyone in both groups would have the same diet, stresses, living conditions, etc. Well, reality is far from the ideal and people tend to live for a long time so either the groups on the medicine and on a placebo need to be huge or the groups need to be followed for decades in order to get statistically valid results to answer the question - does the medicine prevent heart attacks and strokes.

We have thought that blood cholesterol levels served as indicators of what was going on in the blood vessel walls but this has not been shown to be the case for people on Zetia or for women taking Premarin (an estrogen hormone supplement). When the expensive studies were done, there was not a close correlation between the cholesterol levels and the diameter of the blood vessels (for Zetia) or the numbers of heart attacks and strokes (Premarin). We are just more complicated than was thought and these two surprises to medicine may end up having a great influence on how medical research is done and medicines approved in the future.

2 comments:

Tanesia said...

Interesting to know.

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