# another drug question

**URL:** <https://boards.straightdope.com/t/another-drug-question/62124>\
**Category:** Factual Questions\
**Created:** [April 16, 2001, 3:20am UTC](https://boards.straightdope.com/t/another-drug-question/62124 "2001-04-16T03:20:56Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![loislane138](https://avatars.discourse-cdn.com/v4/letter/l/f19dbf/32.png) [@loislane138](https://boards.straightdope.com/u/loislane138)\
**Post date:** [April 16, 2001, 3:20am UTC](https://boards.straightdope.com/t/another-drug-question/62124/1 "2001-04-16T03:20:56Z")

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My sister was once prescribed Xanax (sp?), and there was a warning label on it that read “Do not take with Grapefruit Juice”. Why just grapefruit juice? What if you took it with any other kind of citrus fruit? Or how about anything else that had citric acid in it?

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**Author:** ![LisaRx](https://avatars.discourse-cdn.com/v4/letter/l/77aa72/32.png) [@LisaRx](https://boards.straightdope.com/u/LisaRx)\
**Post date:** [April 16, 2001, 3:34am UTC](https://boards.straightdope.com/t/another-drug-question/62124/2 "2001-04-16T03:34:00Z")

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Actually, there is an ingredient specifically in grapefruit juice or the grapefruit itself that affects the cytochrome-P-450 enzyme in the liver.

Because this drug is metabolized by the liver, the drug will build up in body tissues.

Muscle aches and pains may be a symptom.

I have no idea why grapefruit specifically causes this. I think it has to do with the concentration of limonene(sp?), but don’t remember where I might have read it.

Grapefruit juice affects many other drugs–heart meds, anti-depressants, blood-thinners, anti-fungals, and some anti-biotics. Always ask your pharmacist or doctor if you are a grapefruit consumer.

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**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\
**Post date:** [April 16, 2001, 3:45am UTC](https://boards.straightdope.com/t/another-drug-question/62124/3 "2001-04-16T03:45:38Z")

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I’m proud to note that the grapefruit juice effect was discovered in Canada.

[Look here](http://www.bitemarks.com/dtmodels/faq4.html) for lots of info on this phenomenon.

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**Author:** ![LisaRx](https://avatars.discourse-cdn.com/v4/letter/l/77aa72/32.png) [@LisaRx](https://boards.straightdope.com/u/LisaRx)\
**Post date:** [April 16, 2001, 4:34am UTC](https://boards.straightdope.com/t/another-drug-question/62124/4 "2001-04-16T04:34:01Z")

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Yikes! It humbles me to even try to grasp how complex the human body really is.

It makes me wonder, though, whether the clinical significance of this interaction has been involved in the removal of drugs from the market (i.e. Rezulin®).

Any speculations, Dr Gauss?