
Prescription drugs and grapefruit a 'deadly mix' (2012) - guscost
https://www.nhs.uk/news/medication/prescription-drugs-and-grapefruit-a-deadly-mix/
======
indziektor
And yet it never seems to get enough coverage. The last time I was prescribed
something important, I had no idea I wasn't supposed to have grapefruit or
marmalade with Seville oranges. Luckily it's not my usual fare. The leaflet
did have all sorts of other warnings though, like even for St. John's Wort. I
only found out by a chance comment from a different physician.

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dr_dshiv
Alcohol? In student days, I was always fond of a greyhound: vodka and
grapefruit juice. Placebo effect, or diminished liver capacity?

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imroot
If you've had a liver transplant, grapefruit is on the list of things that you
can never eat again -- it messes with the anti-rejection drugs that you have
to take to suppress your immunological system.

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adrianmonk
I might have expected colchicine
([https://en.wikipedia.org/wiki/Colchicine](https://en.wikipedia.org/wiki/Colchicine))
to be on the list.

It's a fairly harsh drug with a narrow therapeutic window. Getting the right
dosage is already hard enough, as there are some unpleasant (and common) side
effects, and it can also be pretty dangerous to your health. Add something
like grapefruit that throws off the concentration, and things get that much
worse.

EDIT: This HN story link was updated. The list I was referring to above is the
old link:
[https://en.wikipedia.org/wiki/Grapefruit–drug_interactions](https://en.wikipedia.org/wiki/Grapefruit–drug_interactions)

------
bjornsing
My hay fever medication (called Teldanex in Sweden) was withdrawn from the
market in 1998 due to some fatalities when combined with grapefruit. So it
must have been well known long before 2012. I remember feeling quite lucky I
wasn’t into that particular fruit... :P

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Scoundreller
One thing glossed over in these articles is that the impact is mostly on this
enzyme as it exists in the intestines.

There’s less impact on this enzyme as it exists elsewhere in the body
(primarily the liver).

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mirimir
Also, I know that *mycin antibiotics can decrease liver metabolism of statins,
and increase their side effects. In particular, rhabdomyolysis (muscle
damage).[0]

So I suspect that grapefruit isn't the only issue. In that there may well be
interactions among the drug classes listed.

0)
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4006404/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4006404/)

------
neom
I usually Lemon Tek when I take psilocybe: [https://www.mushmagic.com/blog-
magic-mushroom-lemon-tek-a-wa...](https://www.mushmagic.com/blog-magic-
mushroom-lemon-tek-a-way-to-trip-harder-n41)

~~~
collyw
That's different, that converts the psilocybin to psilocin - something that
would go on in your stomach anyway. Adding lemon gets that step out of the way
so it all hits you faster.

------
cwkoss
Similarly, piperdine in black pepper can function as a bioavailability
enhancer

[https://www.ncbi.nlm.nih.gov/pubmed/21434835](https://www.ncbi.nlm.nih.gov/pubmed/21434835)

I read an interesting online report that claimed co-administration of black
pepper and certain essential oils would produce psychoactive effects.

~~~
xtracto
Oooh I read that they use this with tumeric to enhance its absorption. I
wonder if grapefruit would work similarly.

~~~
cwkoss
Interesting! I found this thread which claims that curcumin + black pepper can
function as a reversible MAOI, similarly to caapi or harmala ayahuasca
admixture plants.

[https://drugs-forum.com/threads/curcumin-is-an-effective-
ant...](https://drugs-forum.com/threads/curcumin-is-an-effective-anti-
depresant-and-maoi.140992/)

I've been taking turmeric for an inflammatory issue, will try adding pepper,
thanks!

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drefanzor
I take atorvastatin for high cholesterol; it says don't eat grapefruit on the
side of my medication bottle. I never really thought about why, but this gives
me more reasons to avoid it. Although now I have a huge craving for grapefruit
juice, of course.

~~~
fhars
Then read this article instead:
[https://www.ncbi.nlm.nih.gov/pubmed/26299317](https://www.ncbi.nlm.nih.gov/pubmed/26299317)

~~~
cafard
Thank you. I've been skipping graperfruit juice for years.

------
presidentender
This bit my brother once, on a trip to visit our grandparents. Grandpa would
eat a half grapefruit every morning, believing that the acidity would alkalize
one's system in response and lead (along with frequent alternative chelation
treatments) to better health. We didn't drink the chelation shakes, but we did
eat the grapefruits, since they were there and prepared.

Over the two-week visit, my brother got harder and harder to be around - he'd
always been surly, and he struggled with grandpa's wife, but we'd never
experienced the level of emotional turmoil he went through on that trip. He
self-harmed, sliced his arms up deeply. I stitched him up with the sewing kit
that the resort had mercifully left in the room for us, and we kept the wounds
dressed with neosporin until they healed.

The next stop on the trip was a visit to grandpa's wife's sister, a professor
of neuroscience. She just happened to mention the interaction between
antipsychotics and grapefruit, and it was like a light went on in my brother's
mind. He stopped eating grapefruit and returned to his usual mental state
within a few days.

~~~
loceng
Did none of the doctors prescribing the antipsychotics highlight and caution
against eating grapefruit - hopefully to not consume alcohol either?

~~~
presidentender
I can't speak to his interactions with any doctors. I imagine he forgot. This
was before he was 21, so alcohol wasn't an issue yet.

~~~
loceng
One of the many pitfalls between doctor-patient relationship. Thank you. Hope
he's continued to have relative stability.

------
british_india
Also Fresca is packed with grapefruit juice.

------
benj111
Caffeine is on the list.

So a breakfast of coffee and grapefruit is a medically proven stimulating
start to the day?

~~~
throwaway8941
Sadly, no.

>One study, by Maish and colleagues in Pharmacotherapy 1996, looked at whether
grapefruit juice increased caffeine effects and found little or no difference
in blood concentrations and blood pressure when caffeine was given with and
without GFJ. Other research has confirmed these results. Since specific enzyme
systems most often metabolize similar chemicals, one would not necessarily
expect GFJ to affect other stimulants, but this is far from conclusive.

[https://erowid.org/ask/ask.php?ID=2726](https://erowid.org/ask/ask.php?ID=2726)

~~~
foobarian
IIRC naringin has an indirect effect on coffee, where it inhibits an enzyme
that is involved in metabolizing caffeine. So the outcome is that the effect
of your coffee lasts a lot longer, instead of being more potent.

Edit: Now that I go looking again, there is also evidence against this
conclusion: [https://www.eurekalert.org/pub_releases/2003-04/aps-
rsm04090...](https://www.eurekalert.org/pub_releases/2003-04/aps-
rsm040903.php)

------
journalctl
I avoid grapefruit-anything. I’m on two pretty standard drugs, and they
shouldn’t have any reactions, but I’d rather not take that chance anyway.

~~~
brianpgordon
There's no need to guess; you can look up specifically whether CYP450 enzymes
metabolize your medications (and its metabolites). If not then the answer is
almost certainly that you're safe.

~~~
brianpgordon
I don't know what the downvotes are about. I'm right. This stuff isn't magic.
The mechanism of grapefruit-drug interactions is well-understood.

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amelius
Shouldn't there be a warning label in the Grapefruit section of supermarkets?

~~~
unparagoned
No, because the warning comes with the medecine

~~~
alan-crowe
I've been scrutinizing my package leaflet for tamsulosin. No mention of
grapefruit. Revision date October 2017.

The article links to research from 2012. I'm going to guess that the dangers
turned out to be small and eat my grapefruit for breakfast tomorrow as
planned.

~~~
not_a_doctor2
[https://www.webmd.com/drugs/2/drug-1592/tamsulosin-
oral/deta...](https://www.webmd.com/drugs/2/drug-1592/tamsulosin-
oral/details/list-interaction-details/dmid-141/dmtitle-avoid-grapefruit-
unless-md-instructs-otherwise/intrtype-food)

~~~
alan-crowe
Thank you, very helpful.

------
open-source-ux
Here's a 2012 article from the NHS website on this topic which I think is more
readable than the Wikipedia entry:

[https://www.nhs.uk/news/medication/prescription-drugs-and-
gr...](https://www.nhs.uk/news/medication/prescription-drugs-and-grapefruit-a-
deadly-mix/)

~~~
antsoul
I'd even prefer the Erowid page :
[https://erowid.org/ask/ask.php?ID=2726](https://erowid.org/ask/ask.php?ID=2726)

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myself248
This killed my friend's dad. He was on a bunch of heart drugs and had a
pacemaker and everything, but was generally stable. One day, grapefruit comes
up in conversation with his doctor, who sternly advises him "never eat
grapefruit, it'll mess with your meds!", so he stops eating the grapefruit
he'd been having for breakfast every morning for years.

Which promptly hoses up the finely-adjusted dosages, his symptoms suddenly get
real weird, the situation spirals out of control, and he's dead in 4 days.

Doctors, please don't rush out of the room. Take time to talk to your
patients, and take twice as much time to listen to them. I'm sure he would've
mentioned that detail if he'd had time to find the English words.

~~~
corey_moncure
Doctors want you in and out of the room in 5 minutes or less so they can pull
the insurance money dispensing lever again.

The last physician I had any respect for was my own pediatrician and I had
consulted him on various issues having gone through several GPs that got even
simple diagnoses disastrously, hilariously wrong. Such as telling me the tiny
red lump in my finger was an anthrax infection and notifying the health
department when it was really a small benign vascularity that was removed in a
fifteen minute procedure.

Since my pediatrician retired I just do all my own medical research and order
my own lab tests. The advantage I have is that I have all the insight into my
own body, history, and habits that no doctor these days ever takes the time to
find out. You're just a money pinata. Thank you, here are some antibiotics for
an unspecified pathogen I didn't culture, Alisha will see you at checkout.
Examining the patient? Ain't nobody got time for that.

~~~
ohazi
How do you order a lab test on your own?

~~~
tim58
Find a local lab, ask about submitting a lab, collect then deliver samples.
There isn't anything special that says a blood test has to be requested by a
doctor.

A lab is rarely going to advertise to consumers directly (some startups do
this with mail in tests), but a smaller one will be happy for the bit of extra
business.

~~~
chrismeller
Not necessarily true. In many states if a doctor does not request it your
insurance has no obligation to pay. That doesn’t mean you can’t get it done,
but you’ll be spending hundreds of dollars out of pocket for it.

Also, everywhere I’ve ever lived labs have been a very commercial business.
They advertise constantly about it...

------
HarryHirsch
I wonder why it took the medical profession so long to become aware of the
effect. Piperonyl butoxide, another cytochrome C inhibitor, has been used as
synergist in insecticides since before the war, so it should have occurred to
someone that the plentiful polyphenols in citrus juice could act as cytochrome
C inducers/inhibitors and would have a measurable influence on the
pharmacokinetics of stuff.

~~~
arkades
Just because the article says that the healthcare community is ignorant of it,
doesn’t mean that it’s ignorant of it.

We had to memorize major CYP4503A4 inducers and inhibitors for step exams back
when I was in med school, and memorized metabolic pathways and involved
cytochromes for most major drugs.

Granted, most docs don’t remember all the details long out of med school
(because that’s literally what pharmacists are -for-), but we retain the broad
brushstrokes.

Ain’t new. Just editorializing bs.

~~~
p1necone
Yeah, hasn't "don't eat grapefruit while on birth control" been common advice
for years?

~~~
KineticLensman
Yes, also on medication for high-blood pressure.

(luckily I never had a great liking for grapefruit)

~~~
bgeeek
I sometimes forget because it's not something that I regularly have. I just
have to spend a few moments on my phone before buying certain fruits.

------
hmx48
Its useful for getting the most bang for your buck ouy of expensive
medications.

~~~
burk96
Hah I know right? I do wonder however, is there a use case for these
furanocoumarins found in grapefruit? Perhaps it could make for more efficient
drugs that could (potentially) be cheaper? Or perhaps doctors prescribing
ludicrously expensive drugs (like the cancer drugs listed) could prescribe a
lower dose and a grapefruit concentrate?

~~~
cwkoss
I wonder if grapefruit + reduced dosage could be as effective for primary
effects, but reduce side effects for some drugs.

Would be interesting to find some research in this area: most of what I can
find warns of increased side effects from maintaining constant dosage.

Interesting related info: "Seville oranges, (often used in marmalades), limes
and pomelos also produce this interaction. Varieties of sweet orange, such as
navel or valencia, do not contain furanocoumarins and do not produce this
interaction."

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3589309/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3589309/)

~~~
emmelaich
I've heard it's best to avoid or reduce citrus intake while taking drugs.

I don't know why, but this could be why.

------
ziroshima
Interesting to see this now. As a teenager I experimented with DXM
([https://en.wikipedia.org/wiki/Dextromethorphan](https://en.wikipedia.org/wiki/Dextromethorphan))
as a hallucinogen. You could buy it in powdered form over the internet for a
while, or one could just take corricidin pills or find certain cough syrups
that didn't have acetaminophen. Anyways, it was well known on usenet/IRC at
the time that drinking grapefruit juice prior to ignesting the drug would
enhance its effects.

~~~
hombre_fatal
I had just come out of the peak of an acid trip so intense that I was in the
fetal position under my covers. 1-2 hours had passed but it felt like an
entire day. And it took me 10 minutes just to finally message my friend the
profound admission: "im trippin".

I was pretty hungry after all this and glad the peak was behind me. Got a
grapefruit out of the fridge. Wasn't even halfway through when I found myself
back in the peak. Had to crawl back into my bed where the curtains were closed
and endured another 20 minutes of that.

Grapefruit + <drug> has always been the source of superstitious arguments in
uni among my drug-using friends. Does it enhance the effect? Kill the effect?
Do anything at all? But my acid experience confirmed one pairing beyond all
doubt.

~~~
htfu
Inhibiting CYP3A4 should definitely increase LSD AUC, but it can't magically
conjure more of a substance out of thin air after it's all already entered
your bloodstream - only slow down breakdown. Albeit the apparent effect would
be the former, if ingested beforehand and/or dealing with something with very
slow uptake and high first-pass metabolism.

In any case it's not something that plays out so quickly.

Waving in and out of tripping balls a couple hours in sounds pretty par for
the course, I'd say :)

~~~
cwkoss
Perhaps changing the ph of the bloodstream could also have an effect? Would
presumably increase solubility? Lots of lore around citrus with psychedelics,
seems plausible but would be nice to have more research on the mechanism.

~~~
Scoundreller
If the pH of your bloodstream goes out of whack enough to impact solubility,
you’re long dead.

~~~
cwkoss
Thanks, you are right. Looks like blood pH must remain between 7.35 and 7.45
or else serious negative effects occur. Solubility change would be negligible.

