I had written a reply contradicting the opening post and deleted it. Here is what survived. Widely repeated interaction claim would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
A widely repeated interaction claim that turns out to be unsupported — what changed since Writing it up because I had to work it out twice and would rather nobody else did.
I was wrong about widely repeated interaction claim in a thread last spring and I would like to correct it publicly rather than quietly.
The error was in the units, which changed the conclusion by an order of magnitude. Setting out the corrected version, and the way I now check for that class of mistake.
Marking my place. If it changes for me I will come back and say so.
I had written a reply contradicting the opening post and deleted it. Here is what survived.
Widely repeated interaction claim would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
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.
Nothing here is medical advice and an interaction question is one where the cost of a wrong forum answer is genuinely high. Ask the prescriber or the pharmacist.
Adding it because I spent an afternoon working it out and nobody should have to twice.
Adding the measurement that post #5 says would settle it.
Vitamins: most vitamins have no significant interaction. Fat-soluble vitamins (A, D, E, K) might be affected by the slowing of fat absorption during weight loss, but that is a nutritional consequence rather than an interaction.
The claim is narrower than it sounds, and deliberately so.
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.
Separation timing versus clinically important interaction: a separation timing inconvenience (taking one medication 2 hours before or after another) is not the same as a clinically important interaction. Both can reduce absorption of one or the other, but only true interactions require active management.
Answering the question post #8 raises rather than the one it answers.
Anyone asking an interaction question should list everything, including the things they consider irrelevant. The irrelevant one is the answer more often than chance would suggest.
It took me longer than it should have to see that.
Gastrointestinal symptoms from one compound can mask or mimic an interaction with another. Introducing two changes at once makes attribution impossible, which is an argument for spacing them.
The literature is thinner on this than the confidence in the thread implies.
Two sentences on widely repeated interaction claim and then I will stop, because the rest is speculation and the thread is better without mine.
What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.
Research-use-only compounds have no interaction data of any kind, because interaction studies are done on medicines being developed for use in people.
Where a published interaction study exists it usually reports an area-under-curve ratio, and that number is far more informative than a yes-or-no answer.
I would treat that as a working assumption and revisit it.
Post #18 answers the question as asked. The question underneath it is different.
One caution on widely repeated interaction claim: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
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.
A weak preference rather than a position.
Supplements and herbs: many have no established interaction. Some do. If you are taking something unusual, checking a reference (like a pharmacist) is more useful than guessing from forum discussion.
Noting that I have skin in this question and have tried to discount for it.
Oral medications with a narrow therapeutic index are the ones where that matters most. The interaction is about rate and timing rather than about the total absorbed, in most published cases.
Adding the caveat now so it does not have to be extracted later.
Post #22 is right about the mechanism and I think understates the practical bit.
Two questions I would want answered before drawing anything from the widely repeated interaction claim data above: how were the cases selected, and what happened to the ones that dropped out.
Anticoagulants: no direct interaction with the compounds in this class. Weight loss and body composition changes might affect the clearance or effect of warfarin if you are on it; monitoring INR more frequently during weight loss is reasonable.
The variance between people here is larger than the effect being discussed.
Adding a small correction to the widely repeated interaction claim summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor that matters.
This is the answer, and the reason it is the answer is the more useful part.
Post #25 answers the question as asked. The question underneath it is different.
Alcohol is not contraindicated in the labelling and it does irritate a stomach that is already emptying slowly. There is no published interaction study, and the conservative reading is the obvious one.
Absence of an interaction study is not evidence of no interaction. A great many combinations discussed here have simply never been studied, and saying so is more useful than reasoning from mechanism alone.