Grapefruits?

[xrsm002]

It says on the box of Allegra to avoid grapefruit juice when taking it.

 

[mycrofft]

Include "NIH" when you google stuff.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1873672/

This citation originates from a British pharmacological journal.
http://www.ncbi.nlm.nih.gov/pubmed/15449971

A German one:
http://www.ncbi.nlm.nih.gov/pubmed/9565737

American one, 2002 with interesting backstory (They were looking at alcohol, but the grapefruit juice it was in was active too):http://www.ncbi.nlm.nih.gov/pmc/articles/PMC117477/

Point in all is the effect is indiosyncratically variable between persons.

 

[JPINFV]

[youtube]http://www.youtube.com/watch?v=_NUPRzUcssw[/youtube]

 

[mycrofft]

JPINV, hw cool was that! Thanks.

 

[KellyBracket]

Some people feel strongly about the grapefruit issue, evidently; e.g. "Grapefruit Is Disgusting."

 

[VFlutter]

A question about grapefuit juice and medication is guaranteed to be on every standardized nursing exam.

 

[CANDawg]

Grapefruit suppresses the CYP3A4 enzyme in the digestive tract. With the enzyme suppressed, less drug is metabolized and more is available to enter the bloodstream.

Does this mean the effect would only be seen on drugs administered enterally? Or does grapefruit still have an effect on IV/IM/SQ/etc. routes?

 

[mycrofft]

Sounds like oral meds, but...

What about IV grapefruit? ("May be a vascular irritant"...)

 

[ExpatMedic0]

I have had grapefruit questions on exams in my medic class and I am pretty sure even on the NREMT CBT, or maybe it was my paramedic final, i can not remember it was so long ago.

 

[NomadicMedic]

Sounds like oral meds, but...

What about IV grapefruit? ("May be a vascular irritant"...)

As in... "she could suck a grapefruit through IV tubing?"

 

[mycrofft]

Family forum.....

 

[JPINFV]

It is not all drugs. The drugs are those metabolized by the CYP3A4 enzyme.

Grapefruit suppresses the CYP3A4 enzyme in the digestive tract. With the enzyme suppressed, less drug is metabolized and more is available to enter the bloodstream.

Does this mean the effect would only be seen on drugs administered enterally? Or does grapefruit still have an effect on IV/IM/SQ/etc. routes?

Actually, the first post is misleading at best, wrong at worst. The cytochrome p450 system isn't in the GI proper, it's in the liver. While, yes, that does make it extremely important for oral medications that undergo first pass metabolism (since essentially anything absorbed by the gut first goes through the liver). However the p450 system will also metabolize anything in the blood that it can, not just things fresh from the gut.

 

[CANDawg]

Actually, the first post is misleading at best, wrong at worst. The cytochrome p450 system isn't in the GI proper, it's in the liver. While, yes, that does make it extremely important for oral medications that undergo first pass metabolism (since essentially anything absorbed by the gut first goes through the liver). However the p450 system will also metabolize anything in the blood that it can, not just things fresh from the gut.

I vote JPINFV gets a free Premium+ membership for that answer.

:wub:

 

[mycrofft]

+++ yes

 

[TheLocalMedic]

The grapefruit question is an interesting one. Like many of you I have heard of the dangers of mixing grapefruit juice with medications, but until recently I haven't really thought about it much.

However, a few weeks ago I had an OD call for an elderly male who had taken his usual dose of oxycodone but was in resp failure. Narcan fixed the problem and we transported, but I was interested as to why this supposed "normal" dose of his meds would have caused an overdose. The only thing that I and the ED could come up with is that he started drinking a bunch of grapefruit juice to help him pee. Apparently the grapefruit juice increased the potency of his oxycodone which caused the overdose.

Interesting learning moment. The family had mentioned that he drank a lot of grapefruit juice, but apparently the significance was lost on me as to the correlation between the juice and the medication...

 

[rogersam5]

Actually, the first post is misleading at best, wrong at worst. The cytochrome p450 system isn't in the GI proper, it's in the liver. While, yes, that does make it extremely important for oral medications that undergo first pass metabolism (since essentially anything absorbed by the gut first goes through the liver). However the p450 system will also metabolize anything in the blood that it can, not just things fresh from the gut.

I wouldn't go as far as to say it is wrong, CYP450 3A4 is found in the mucosa of the GI track but you are right in that the bulk of concern for metabolism occurs in the liver, and we wouldn't actually care that much clinically in this case other than knowing our dosing can be massively messed up and possibly over the therapeutic range causing problems.

Now anyone want to venture a guess as to how daily use of NSAIDS may increase the risk of asthma?