# Why can't you have grapefruit when taking Xanax? **URL:** \ **Category:** Factual Questions\ **Created:** [April 25, 2004, 4:42am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883 "2004-04-25T04:42:19Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![oriegirl44](https://avatars.discourse-cdn.com/v4/letter/o/f14d63/32.png) [@oriegirl44](https://boards.straightdope.com/u/oriegirl44)\ **Post date:** [April 25, 2004, 4:42am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/1 "2004-04-25T04:42:19Z")
I recently started taking Xanax and on the bottle it has a warning that says not to eat grapefruit or drink grapefruit juice while taking this medicie…why is that? ---
**Author:** ![The\_Asbestos\_Mango](https://avatars.discourse-cdn.com/v4/letter/t/edb3f5/32.png) [@The\_Asbestos\_Mango](https://boards.straightdope.com/u/The_Asbestos_Mango)\ **Post date:** [April 25, 2004, 5:00am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/2 "2004-04-25T05:00:14Z")
I’m not sure about the specfic chemical details, but there’s a substance in grapefruit that ramps up the effects of the Xanax. I actually used to wash down Xanax with grapefruit juice… not something I’d recommend, I’m just saying, is all… ---
**Author:** ![Eva\_Luna](https://avatars.discourse-cdn.com/v4/letter/e/e495f1/32.png) [@Eva\_Luna](https://boards.straightdope.com/u/Eva_Luna)\ **Post date:** [April 25, 2004, 5:07am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/3 "2004-04-25T05:07:50Z")
Grapefruit juice can have drastic effects on the absorption of some medications: [http://psa-rising.com/eatingwell/citrus\_effects.html](http://psa-rising.com/eatingwell/citrus_effects.html) [http://psa-rising.com/eatingwell/citrus\_effects.html](http://psa-rising.com/eatingwell/citrus_effects.html) [http://www.somersetmedicalcenter.com/18448.cfm](http://www.somersetmedicalcenter.com/18448.cfm) [http://edis.ifas.ufl.edu/BODY\_FS088](http://edis.ifas.ufl.edu/BODY_FS088) …as you can see, it’s not just Xanax. ---
**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 25, 2004, 5:12am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/4 "2004-04-25T05:12:37Z")
It’s not at all specific to Xanax. Grapefruit juice interacts with numerous drugs (and increases their blood concentrations by a variety of mechanisms). [Here is a concise chart showing some of the interactions](http://www.fhma.com/grapefruit.htm). ---
**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 25, 2004, 5:13am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/5 "2004-04-25T05:13:39Z")
That was actually a simul-post. Sorry. ---
**Author:** ![Freejooky](https://avatars.discourse-cdn.com/v4/letter/f/ba8739/32.png) [@Freejooky](https://boards.straightdope.com/u/Freejooky)\ **Post date:** [April 25, 2004, 6:00am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/6 "2004-04-25T06:00:01Z")
Interesting. I took Xanax almost daily for nearly 2 years and never got one of these warnings on my bottles. ---
**Author:** ![paa3838](https://avatars.discourse-cdn.com/v4/letter/p/9de053/32.png) [@paa3838](https://boards.straightdope.com/u/paa3838)\ **Post date:** [April 25, 2004, 12:19pm UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/7 "2004-04-25T12:19:26Z")
It has to do with metabolic enzymes… grapefruit juice inhibits cytochrome P450 expression, which can increase the effect of some medications. The labeling on Xanax is fairly new. ---
**Author:** ![Reader99](https://avatars.discourse-cdn.com/v4/letter/r/df788c/32.png) [@Reader99](https://boards.straightdope.com/u/Reader99)\ **Post date:** [April 26, 2004, 3:32am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/8 "2004-04-26T03:32:31Z")
i’ve read about this phenomenon, and i’ve had this question: instead of telling people to \*avoid \* grapefruit juice with their medication, why not give them a lower dose of medicine and tell them to take it _with_ grapefruit juice? in general, isn’t it healthiest to take the \*lowest \* effective dose of a medication? ---
**Author:** ![Freejooky](https://avatars.discourse-cdn.com/v4/letter/f/ba8739/32.png) [@Freejooky](https://boards.straightdope.com/u/Freejooky)\ **Post date:** [April 26, 2004, 3:36am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/9 "2004-04-26T03:36:27Z")
Well, I know the pharm. compananies love to offer their meds in comically-large doses, so that they’re more marketable. The reasoning is that if one guy responds well to 5 mg. but the next guy needs 25, making the lowest available dosage 75 mg. ensures that it’s enough for everyone. Of course, this is ridiculous, as higher mg’s all but guarantee more (bad, undesriable) side effects, and the vast majority (something like 80%+) of people respond well to much lower doses than are available. ---
**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 26, 2004, 3:48am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/10 "2004-04-26T03:48:01Z")
In theory you could do that but it’s frought with danger insofar as there is no standard amount/potency of grapefruit, whereas there is a standard, a very well defined one, of medication. Rather than risk the uncertainties of various types/sizes/origins of grapefruit, why not just avoid it altogether? And, although it’s true you want to use the lowest effective dose of a drug, that’s because you generally want the lowest effective blood level of that drug. If you wind up with the _same_ blood level by either a) giving a higher dose and no grapefruit or b) a lower dose but with grapefruit, and the latter runs the risks associated with non-standardization, what’s the gain? One way your idea could be justified is if the medicine was _very_ expensive so that it paid to screw up the drug’s breakdown/clearance in order to use a lower dose of it (and save money). That was done [here](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7637723) (with ketoconazole playing the role of grapefruit). ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [April 26, 2004, 4:17am UTC](https://boards.straightdope.com/t/why-cant-you-have-grapefruit-when-taking-xanax/241883/11 "2004-04-26T04:17:17Z")
> [@KarlGauss](#): > > In theory you could do that but it’s frought with danger insofar as there is no standard amount/potency of grapefruit… Plus there’s person to person variation in the amount of cytchrome p450-3A4 (and other affected p450s) in liver tissue, and differences in the extent to which inhibitors induce production of _more_ p450. When the drug is cheap, there’s no good reason to open up a big old can of worms in order to minimize the effective dose.