# Valium and Grapefruit **URL:** \ **Category:** Factual Questions\ **Created:** [January 4, 2006, 2:58pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395 "2006-01-04T14:58:41Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [January 4, 2006, 2:58pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/1 "2006-01-04T14:58:41Z")
My doctor has me on Valium for back pain (he says that in low doses it’s a muscle relaxer). The bottle has a warning on it advising me not to eat grapefruit or drink grapefruit juice while taking this medicine. My favorite diet soft drink, Fresca™, lists “Concentrated Grapefruit Juice” third on its list of ingredients. Is Fresca™ contraindicated for someone on Valium therapy? What’s likely to happen if I drink it? TIA ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [January 4, 2006, 3:37pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/2 "2006-01-04T15:37:55Z")
Grapefruit juice affects how your body absorbs and utilizes Valium (diazepam). [http://www.powernetdesign.com/grapefruit/references/ref41abstract.html](http://www.powernetdesign.com/grapefruit/references/ref41abstract.html) > [@](#): > > Interaction between grapefruit juice and diazepam in humans. > > Ozdemir M, Aktan Y, Boydag BS, Cingi MI, Musmul A. > Department of Pharmacology, Medical Faculty, University of Osmangazi, Eskisehir, Turkey. > > Grapefruit juice has been reported to markedly improve the bioavailability of triazolam, midazolam, terfenadine, cyclosporine and several dihydropyridine calcium channel blockers including felodipine, nifedipine, nitrendipine and nisoldipine. Because these drugs are metabolized by the hepatic cytochrome P450 isozyme (CYP) 3A4, the inhibitory effect of grapefruit juice is thought to results from inhibition of CYP3A4. In this study, our aim was to investigate the effects of grapefruit juice on plasma concentrations of diazepam. Eight healthy male and female subjects participated in this study. Oral (5 mg) diazepam was administered with either 250 ml water and grapefruit juice. Blood samples were collected for a 24 h period, and whole blood concentrations of diazepam were measured enzyme immunoassay. The mean AUC(0-24) of diazepam was increased 3.2-fold (P \< 0.001) and Cmax was increased 1.5-fold (P \< 0.05) by the grapefruit juice. Grapefruit juice postponed the tmax of diazepam from 1.50 h to 2.06 h (P \< 0.01). > > Eur J Drug Metab Pharmacokinet 1998 Jan-Mar;23(1):55-9. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [January 4, 2006, 4:59pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/3 "2006-01-04T16:59:35Z")
My WAG is that it’s probably very little risk. Every case I’ve heard of toxicity resulting from grapefruit juice and drugs involved drinking quite a bit of grapefruit juice; I doubt the amount present in a can of Fresca is all that high. Which doesn’t necessarily mean I’d risk it myself . . . ---
**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:** [January 4, 2006, 5:30pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/4 "2006-01-04T17:30:51Z")
> [@Excalibre](#): > > My WAG is that it’s probably very little risk. Every case I’ve heard of toxicity resulting from grapefruit juice and drugs involved drinking quite a bit of grapefruit juice; I doubt the amount present in a can of Fresca is all that high. > > Which doesn’t necessarily mean I’d risk it myself . . . Fair enough, but at least [one source](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15449971&query_hl=5&itool=pubmed_DocSum) suggests that even a single glass of grapefruit juice might cause drug toxicity. Another point is that people have varying amounts of (intestinal) CYP3A4 to inhibit. Those with already low levels will hardly be affected by grapefruit juice. OTOH, those with high levels have a lot to lose. ---
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [January 4, 2006, 5:37pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/5 "2006-01-04T17:37:14Z")
> [@KarlGauss](#): > > Fair enough, but at least [one source](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15449971&query_hl=5&itool=pubmed_DocSum) suggests that even a single glass of grapefruit juice might cause drug toxicity. I think I’d have to drink at least a 12-pack, if not more, of Fresca™ to get the amount of grapefruit juice that’s present in one glass of straight juice. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [January 4, 2006, 6:37pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/6 "2006-01-04T18:37:41Z")
> [@KarlGauss](#): > > Fair enough, but at least [one source](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15449971&query_hl=5&itool=pubmed_DocSum) suggests that even a single glass of grapefruit juice might cause drug toxicity. > > Another point is that people have varying amounts of (intestinal) CYP3A4 to inhibit. Those with already low levels will hardly be affected by grapefruit juice. OTOH, those with high levels have a lot to lose. Another thing to consider is of course the toxicity of the drug in question. I don’t know how acutely toxic valium is - is it easy to overdose on it? If the window between therapeutic and toxic is small enough, than even a small amount of grapefruit juice might decrease metabolism enough to be problematic. ---
**Author:** ![alaricthegoth](https://avatars.discourse-cdn.com/v4/letter/a/4bbf92/32.png) [@alaricthegoth](https://boards.straightdope.com/u/alaricthegoth)\ **Post date:** [January 4, 2006, 8:19pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/7 "2006-01-04T20:19:27Z")
I have seen grapefruit described as a “powerful” cytochrome 450 inhibitor. I wouldn’t roll the dice on the fresca. ---
**Author:** ![TheBoneyKingofNowhere](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@TheBoneyKingofNowhere](https://boards.straightdope.com/u/TheBoneyKingofNowhere)\ **Post date:** [January 4, 2006, 9:27pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/8 "2006-01-04T21:27:51Z")
I remember reading about a high school wrestler who had mysteriously died during an after school workout. He was breaking rules by wearing plastic under his sweats, but so were the others. The coaches/school were in big trouble, but it was later discovered that he had taken his (I think it was new) medication with a bottle of grapefruit juice earlier in the day. The combination of the workout plus the prescription and the grapefruit juice was too much for the otherwise healthy high school kid. ---
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [January 4, 2006, 11:04pm UTC](https://boards.straightdope.com/t/valium-and-grapefruit/338395/9 "2006-01-04T23:04:48Z")
I just noticed that there is a duplicate of this thread in Great Debates. I made a mistake. Here’s what happened: I posted the GD thread early this morning, thinking I was in GQ. When I checked GQ an hour or so later and didn’t see my thread, I re-posted it, assuming that there was a hamster issue, unaware that I had originally (and accidentally) posted in GD. Bottom line: a simple oversight and not an attempt to cross-post. Sorry about that.