Grapefruit/drug interactions!?!

[koa]

Today I bought some grapefruit juice and promptly drank like four glasses.  I was so excited to be drinking something so fresh and healthy... or so I THOUGHT.

 

Then my girlfriend suggested that I check to see if it interacted with any drugs.  I was like, um, are you kidding?  Grapefruit juice?

 

Holy shit, grapefruit interacts adversely with about 80 medications! 

 

Luckily none of the ones I take were listed, except possibly Ativan, which I've stopped taking lately. 

 

But I'm still worried that it interacts with the drugs I'm taking and the researchers just don't know about it.  I was really afraid to take my Risperdal... but did anyway.

 

I mean, am I being unreasonable?  "They" only found out about these interactions like 15 years ago, by accident, when researchers were studying the effects of alcohol, which in the study they mixed with grapefruit juice.  Is it so weird to think that maybe "they" haven't discovered everything that grapefruit juice interacts with yet?

 

 

[mellifluous]

holy fuck! i just googled it to see about mine and though only a couple i'm at all prescribed now are in this list: http://en.wikipedia.org/wiki/Grapefruit_drug_interactions

 yeah, now i'm sitting here, like, maybe the ones i take that aren't on there just aren't KNOWN to react...but who wants to guinea pig that?! not it. now i wish i could undo my last injection until i can figure this out... 

 

did you ask a pharmacist/physician about the risperdal yet? 

[melissaw72]

My pdoc told me about this.  A few of mine interact with grapefruit juice ... if I drink it, it builds up the med in my blood and I get side effects.  Abilify is a big one for me that I can't have grapefruit juice with, or if I do on a regular basis, would need to lower the dose.

[Cacia]

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Edited July 8, 2013 by Cacia

[Luna-]

There is a good thread about it on CrazyMeds: here

[rowan77]

I know that grapefruit interacts with Seroquel. Also when I was on carbamezapine I found out that grapefruit interacted with it too

[bookgirl]

I HATE that some of my meds interact with grapefruit. I love grapefruit. I accidentally ate grapefruit sorbet a couple weeks ago because I'd forgotten. 

[olga]

Grapefruit interacts with the common cholesterol drugs, called statins, in addition to some of the psych drugs.  However, some of the research they did involved giving rats QUARTS of juice, which most people would not ingest.

 

koakua, it is always better to eat the fruit rather than drink fruit juice.  Most juices are loaded with sugar, even though it is natural sugar from the fruit.  The juices are calorie-dense, so an appropriate serving is about 6 ounces.  Measure that out sometime---you'll be shocked at how small it is.

 

You're much better off to drink four glasses of water, and then eat half of an actual grapefruit.  Eating half a grapefruit a day will probably have very little effect on any of the drugs you are taking.

 

Moderation in all things, koakua.  Drinking a quart or a half-gallon of anything is rarely a good idea.  Except water, of course.

 

olga

[koa]

Olga,

 

I'm aware that juice has a lot of sugar.  I rarely buy it... this was sort of an impulse thing... but yeah, as you are aware from reading how much alcohol I drink, I struggle sometimes with moderation.

[olga]

You are not alone in that, my friend.  I think many of us here have issues with doing things in moderation.  If I get a pound of chocolates for a gift, they are gone in a day or two.  sigh.

 

olga

[lysergia]

just once i'd like to have a food interaction from something i don't like!  i really really miss grapefruit juice.  and i miss cheese and olives a LOT too (MAOI diet).

[Parsley]

Grapefruit inhibits the enzymes that break up drugs, the amount of a drug put into tablets is calculated to allow for about half of it to be broken down by digestive enzymes. So if you inhibit those enzymes you will find yourself unwittingly overdosing. I would be more specific but my brain is full of cotton wool... I did a mad internet research a while back... I probably found a lot of my sources through a wikipedia page about grapefruits or something. I usually follow wikipedia sources, to check if they are a reliable cited source or just another vague article. I think I'm making sense but I may have stopped making sense.

[Kaashii]

It makes sense, Parsley.  What you're referring to with the limited amount of drug that gets into your circulation is called the "first pass effect".  There's all kinds of fun calculations you can do to figure out how much of the drug you lose at each step of the metabolism, how much you wind up excreting in your bodily waste and whatnot, but it's easiest to say that the liver plays a pretty important part in carrying the drug into your bloodstream and breaking many of them down into the compounds that actually work.  (The ones that get broken down, a prime example would be Rispderal.  Risperdal is what's called a prodrug, which means it needs to be broken down by the body into the active compound, which is actually what Invega is.)  The % of what is actually available of the drug is the bioavailability, which is something you'll see if you nose around on the prescribing data sheets or the more advanced readings somewhere like drugs.com.  (Warning:  You'll see some pretty low numbers on some drugs.  It's not a sign that it's ineffective.  It just means that the body doesn't absorb the entire amount, but the drug companies have calculated how much needs to be in the pills to receive a proper dose.  It's easy to look and want to freak out when you see a bioavailability of 20% or less, but it's not something to freak out over.) 

 

This page of course notes from the U. of Waterloo gives a not-TOO-heavy explanation of how orally administered meds are metabolized.  It's a little thick, but it may help if someone's curious.

Definition of a prodrug in case someone wants a source on that.

 

There's a LOT of information about the substances that inhibit or induce the activity of the liver enzymes.  This is the best that I can find about the CYP450 enzymes that are important for breaking down drugs that isn't TOTALLY bogged down with pharmababble or just from Wikipedia.  Having a harder time finding something about grapefruit juice and the CYP3A4 enzyme that isn't REALLY technical.  This is the best I can do at the moment for some form of source to back up Wikipedia's articles (Number 1, Number 2) that states that grapefruit juice DOES interfere with drug metabolism without it being ridiculously technical.  It's still very thick, but it backs up the Wikipedia, at least.

 

A lot of drugs don't seem to have a warning about grapefruit juice on the labels where I live, and surprisingly, half of my info sheets from the pharmacy don't either.  When in doubt, call your pharmacist to find out for sure if it does.  With the psych meds in general, it seems a safer bet to stay away from it and find other tasty juices to enjoy.

 

(Obvious disclaimer:  I am NOT a doctor or pharmacist, just a lay person with too much time on her hands and a fascination with pharmacology.  Nothing I say is a substitute for the advice of an actual qualified health professional.)

[saveyoursanity]

I just avoid grapefruit juice entirely.  Although that's easy as hell because I hate it.