Monday, January 9, 2012

Grapefruit Juice and Drug Bioavailability

I was flipping through my collection of drug-related books and articles and I found that quite a few were related to grapefruit juice. Grapefruit juice? That sounds like my experience with mangoes amplifying a trip, which I wrote about here if you're curious. I thought maybe there was some correlation, so I investigated furthur.

Drug bioavailability is the percentage of a drug that you ingest that actually makes it to its biological target. When you take a drug orally, whether it's LSD or aspirin, some of it is metabolized (digested & taken apart) before it can reach your bloodstream. If you inject a drug, its bioavailability is 100%. Grapefruit juice will increase the bioavailability of certain drugs by interfering with the metabolizing process, and therefore increase their effectiveness and potency.

Scientists first discovered this when they were experimenting with the effects of mixing alcohol and another drug, felodipine. With their test subjects, they used grapefruit juice to mask the flavor of the alcohol mix as they drank it, and it ended up increasing the bioavailability of the felodipine. Even a single glass of grapefruit juice, taken within 24 hours of the administered dose, will create these effects.

Other scientists found that cytochrome, which occurs naturally in the small intestine and is responsible for the metabolizing of certain molecules, is what the grapefruit juice inhibits. Though it's not known exactly what chemical in the juice causes it, they have narrowed it down to a few theories: naringin (which doesn't occur in other fruit juices and is known to limit metabolism), quercetin, kaempferol, furanocoumarians, and bergamottin. In case you were curious.

What does this mean for recreational drug use? Well, unfortunately, not much. Though it increases bioavailability in a variety of substances, it doesn't do so for all of them. One chemical it does affect is setraline, also known as Zoloft. It is a Selective Serotonin Reuptake Inhibitor, or SSRI, meaning that it prevents your body from reabsorbing and metabolizing serotonin, a neurological chemical that plays a part in keeping you happy. By keeping more serotonin active in your body, your mood stabilizes. By increasing the bioavailability of SSRIs, grapefruit juice makes them more potent. LSD also functions by serotonin-- it blocks serotonin's receptors because of its similar shape. Therefore, grapefruit juice shouldn't have an effect on LSD and related hallucinogens, unless you're taking an SSRI already, and then it will make the LSD even less effective.

Of course, I am not a biologist or a chemist; just a careful reader and researcher. If I drew an incorrect conclusion or you know something more on the matter, please tell me in the comments and I will edit the post.

tl;dr: To the best of my knowledge, grapefruit juice will not make hallucinogens any more potent, and will actually decrease potency furthur if one is already taking an SSRI.


Food-drug interaction: grapefruit juice augments drug bioavailability-- mechanism, extent and relevance
by A. Dahan and H. Altman
Enhanced by Zemanta


  1. That is amazing! I had no idea the impact (delicious) grapefruit has on bioavailability of drugs!

    ~ Tiffany

    Transfer of Health
    Healthy Living and Recipes

  2. do you mean that grapefruit could replace SSRI medications ?

    1. No, what I mean is that if you are already on SSRI medications and you drink a glass of grapefruit juice, they will be more effective. The compounds are not already in the grapefruit juice; all the juice does is help them get where they're going better.

  3. taking grapefruit juice or fruit and SSRI´s can cause the SSRI´s in the bloodstream to build up to a level that can be toxic and should not be experiemented with

    1. Thank you, I should have made that more clear. By more effective, I didn't always mean better. Serotonin Syndrome is serious and shouldn't be risked.

  4. what about ergo genic aids and grape fruit -- like if I took creatine and grapefruit together would I absorb more creatine???

    obviously not a psychopharmacologist for that matter.
    judging from the comments on this page, that means nothing to the people reading it.
    yes grapefruit can slow metabolism on certain drugs, if you take X every day at 8am (and its 1/2 life is 24hrs) then take it with grapefruit you can increase the 1/2 life to say 36hrs, over time this builds up, while your tolerance also increases.
    there are many cases of drug overdoses like this, where people did not notice increased effects, or others. and they were fine for months, but over time, the level built up PAST the LD50 (lethal dose for 50%). and THEY HAVE DIED.
    your misguided-partial story- and the publics misunderstanding of half-life contribute to many deaths.
    half life in a constant, meaning if the half life is 8hrs 8hrs after ingestion 50% of the drug is out of your system, in the next 8hrs, 1/2 of the 50% is out of our system, in 24hrs 12.5% of the original dose is still in your system. and so on and so on.


  7. grapefruit juice are very good for you with their high levels of vitamin C and other nutrients

  8. The unique chemical structure of naringin endows it various biological activities, and thereby it shows prominent utilization potentiality in many fields with tremendous economic value. naringin grapefruit


Thank you for commenting on this post! Remember, be polite!