How Does The Entherohepatic Cycle Influence Levels Of Drugs Such As Simvastatin In The Blood?

[adidash]

How does the entherohepatic cycle influence levels of drugs such as simvastatin in the blood?

[Sqad]

Drugs taken by mouth have to be absorbed via the intestine and into the portal system of the liver, having to clear many hurdles.

just read this abstract which will explain it in a simple fashion.

http://www.ncbi.nlm.nih.gov/pubmed/14705863

[Peter Pedant]

http://www.ncbi.nlm.nih.gov/pubmed/12162761

different ref which is quite helpful

Go the lecture on this and read the chapter

no tricks

They want you to describe the hepatic cycle
what factros affect it - see abstract
and then apply the principles to simvastin

the effect is to prolong apparently

the possible effect of converting a prodrug into an active drug isnt part of this essay as far as I can see from the literature

[EdgeofDarkness]

The short answer, without reading any links, is as follows.
The amount of an ingested drug dose getting into the blood stream is variable, according to what food has been eaten, when, the efficiency of digestive organs, the efficiency of liver...blood levels of drugs administered intravenously can be more predictable.

[germinalvelocity]

It's been over a decade since med school but let's see if I can remember this stuff "off the cuff".
The enterohepatic cycle can be a crucial element in the metabolism/ catabolism of certain drugs. We are limiting ourselves to drugs taken orally (that's the "entero" part). In the liver there is an extensive set of enzymes known as the cytochrome P450 system. There are many drugs that are more "cytochrome active" than others. An excellent example of this would be the drug paroxetine (Paxil) taken for depression. Well if someone were on this drug and were to take an over-the-counter cold remedy containing dextromethorphan, they could very well end up with a phenomenon known as "serotonin syndrome". You may have also heard about this sort of thing happening to someone who drinks green tea or grapefruit juice while on a certain drug. It can be life-threatening. This is where we can run into drug levels becoming toxic, as if say grapefruit juice is unknowingly taken it will "compete" with the drug for receptor sites, thus making the serum levels of the drug too high or potentially toxic.
Also, many of the drugs that are taken orally or given parenterally (IV) are not the actual drug at all but a "pro-drug" that is dependent upon these hepatic enzymes to metabolize/ convert the pro-drug into the active or "therapeutic" form of the drug.