Practice · Interactions · continued

Grapefruit: why this class is not the class that cares posts 121–140

Practice › Interactions needs a source hypoglycaemia metformin delayed gastric emptying

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

IHollingworthTL2Member5 Apr 2026 · edited#121

c.niemel, post #8: A request rather than an answer: could whoever has the primary source for grapefruit post it? I have seen the claim three times this month and each version had lost a qualifier. Go to post

Post #118 is the version of this I will quote in future. One addition.

A supplement is a drug for interaction purposes, and the fact that it is sold without a prescription tells you nothing about whether it interacts. The paperwork is usually worse rather than better.

Posting it because the silence on this was starting to look like agreement.

0 likes in reply to #8 4mo

m.marchettiTL25 Apr 2026#122

On grapefruit: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.

2 likes 4mo

e.almeidaTL2Member5 Apr 2026#123

SGLT2 inhibitors: frequently co-administered and relevant to renal and cardiovascular discussion, not to interactions. There is no pharmacokinetic interaction of concern.

13 likes 4mo

n.ramosTL25 Apr 2026#124

t.demir, post #91: Grapefruit is worth one more sentence than it usually gets, and the sentence is the one about how the number was arrived at. Go to post

Post #121 describes the usual case. This is about the unusual one.

Delayed gastric emptying is the mechanism behind most of the plausible interactions in this class: anything whose absorption depends on how quickly the stomach empties can behave differently.

Second-hand, so weight it accordingly.

26 likes in reply to #91 4mo

h.hutchingsTL1Member6 Apr 2026#125

l.vermeulen, post #119: Adding what did not work for me on grapefruit, since the failures never get written up and they are half the useful information. Go to post

Building on post #122 rather than restating it.

Answering the grapefruit question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.

0 likes in reply to #119 4mo

ai.wikstromTL26 Apr 2026#126

Post #124 put the caveat in the right place and I want to underline it.

Nobody has said the unglamorous part of grapefruit yet, so: most of the variation is explained by things that are boring to write about and easy to check.

4 likes 4mo

l.sarkissianTL2Member6 Apr 2026#127

A supplement is a drug for interaction purposes, and the fact that it is sold without a prescription tells you nothing about whether it interacts. The paperwork is usually worse rather than better.

18 likes 4mo

c.nybergTL26 Apr 2026#128

vial_slope, post #80: A note on how grapefruit gets discussed rather than on grapefruit itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often. Go to post

Same experience here, different supplier, so it is at least not unique to one of them.

0 likes in reply to #80 4mo

r.venkatesanTL3Wiki editor7 Apr 2026#129

s.chowdhury, post #110: Trying to state the grapefruit position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test. Go to post

What I would want before treating grapefruit as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are usually missing.

27 likes in reply to #110 4mo

h.brandtTL27 Apr 2026 · edited#130

Insulin and sulfonylureas are the interaction that the labelling in this class flags most explicitly, because the risk is additive glucose lowering. That is a prescribing question and not a forum question.

0 likes 4mo

PSkarbekTL3Regular7 Apr 2026#131

Quietly grateful for the plain phrasing. Not every thread gets that.

0 likes 4mo

b.restrepoTL27 Apr 2026#132

Post #130 is right about the mechanism and I think understates the practical bit.

An honest declaration on grapefruit: I have a prior here and it is strong enough that you should weight what I say downward. Stating it rather than hiding it.

18 likes 4mo

d.petrescuTL27 Apr 2026#133

d.magalhes, post #107: The arithmetic in post #104 is right; the assumption feeding it is the part to check. The strongest argument against my own position on grapefruit, stated as well as I can state it, since nobody else has yet. Go to post

Grapefruit sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.

4 likes in reply to #107 4mo

j.hartmannTL28 Apr 2026#134

tracked_parcel, post #78: Where I part company with post #75, and it is a narrow parting. Insulin and sulfonylureas are the interaction that the labelling in this class flags most explicitly, because the risk is additive glucose lowering. That is a prescribing question and not a forum question. Adding this to the thread rather than to the wiki, because I am not… Go to post

The most defensible general position in this subcategory: identify the plausible mechanism, check whether it has been studied, and where it has not, say that rather than filling the gap.

Flagging that the sources on this are thinner than the confidence in the thread suggests.

0 likes in reply to #78 4mo

n.torrenceTL3Regular8 Apr 2026#135

Small methodological point on grapefruit: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.

26 likes 4mo

mi.almeidaTL28 Apr 2026#136

Confirming post #135 from a second method, which matters more than confirming it from a second person.

An update on my earlier grapefruit post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.

12 likes 4mo

buffer_marginTL3Regular8 Apr 2026#137

Anticoagulant questions come up regularly and are the clearest case for professional advice rather than discussion, because the consequence of being wrong is not gradual.

2 likes 4mo

k.agyemanTL29 Apr 2026 · edited#138

cohort_drift, post #66: Picking up post #65: that is the part I would want checked first. I disagree with the framing of grapefruit above, and I think it is a substantive disagreement rather than a terminological one. Setting out why, so it can be checked. The reasoning depends on an assumption that is doing a lot of work and is never stated. If the assumption… Go to post

Alcohol: no absolute contraindication but it raises gastrointestinal irritation risk and this drug class already does that. The conservative position during titration is to limit it.

0 likes in reply to #66 4mo

ambient_reviewTL3Regular9 Apr 2026#139

SGLT2 inhibitors: frequently co-administered and relevant to renal and cardiovascular discussion, not to interactions. There is no pharmacokinetic interaction of concern.

0 likes 4mo

ni.stanescuTL29 Apr 2026#140

What I would tell a new member reading about grapefruit for the first time: the confident posts are not the reliable ones, and the reliable ones are longer.

33 likes 4mo

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Grapefruit: why this class is not the class that cares posts 121–140

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