I'm a 6th form student and having learnt a bit about cholesterol at AS I was wondering about drugs used to lower its levels in the blood, as I am hoping to pursue a career in pharmacy. Could someone help me get a better understanding of this?
I found that a common drug treatment for high cholesterol is the use of statins such as simvastatin and atorvastatin. From what I've read/know from AS, they competitively inhibit an enzyme involved in the snythesis of cholesterol in the liver and that this leads to increased LDL receptors on cells to increase uptake of cholesterol from the blood (to be broken down in cells and used structurally in the membrane and to make things like steroid hormones and bile).
However, if they do exactly the same thing, why there are two different drugs used to treat it in the first place and why do dosages need to be different? Basically, what exactly is it about the two drugs that makes them different?
Also, I understand the idea of competitive inhibition with the enzymes, but how exactly would that lead to an increased number of LDL receptors? Is there a mechanism that leads to this or is it just relative to the new amount of cholesterol in the blood because of the inhibition?
I'm sorry if the answers seem really obvious/these are stupid questions...
Thanks in advance for any help.
- Thread Starter
- 28-11-2010 14:35
- 03-12-2010 11:00
The different drugs are simply different molecules, and as they do the same thing they are classed as statins. As far as we know, they do exactly the same thing. The things that vary are:
1) Their affinity for the binding site
2) Their ability to inhibit once bound (efficacy)
3) How the body breaks them down or excretes them (half life)
4) ability to cross certain barriers (although i think they are mostly similar for statins)
5) toxic dose and side affects.
Doctors need to get the right combination of these factors to get the optimum treatment. Often there is a lot of individual variation, so if a patient experiences bad side affects with one drugs GPs may prescribe another to see if its better (not sure how much this applies to statins specifically).
As for the mechanism of action, there may be a mechanism by which statins increase LDL proportion, but i don't think one has been shown. As far as we know, the increase due to the reduced liver cholesterol meaning the liver makes LDL proteins to gather cholesterol from elsewhere e.g. blood stream. "new amount of cholesterol in the blood" doesn't really make sense - statins act on the liver and affects on the blood are secondary to that.