This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
On post #57 — agreed on the reasoning, with one qualification.
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.
That is a description of practice, not a recommendation of it.
Distinguishing three things in the widely repeated interaction claim discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both.
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 a source would improve this post and I do not have one to hand.
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.
Not disagreeing with anyone above, just adding the bit I keep having to look up.
Adding the measurement that post #65 says would settle it.
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.
It is worth stating the boring hypothesis before the interesting one.
Where I part company with post #65, and it is a narrow parting.
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.
I think the widely repeated interaction claim question is answerable and has not been answered, which is a more optimistic position than most of this thread.
The arithmetic in post #69 is right; the assumption feeding it is the part to check.
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.
Reading it back, the second half matters more than the first.
Helpful, and short, which on this subject is harder than long.
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.
A partial answer, offered because a partial answer beats none.
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.
Narrowing post #73, because the general version has more than one answer.
SGLT2 inhibitors: frequently co-administered and relevant to renal and cardiovascular discussion, not to interactions. There is no pharmacokinetic interaction of concern.
Two sources, same conclusion, and I could not rule out that one copied the other.
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.
It cost nothing to check and would have cost something not to.
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.
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.
I would put this at better than even and not much better.
Post #79 is the version of this I will quote in future. One addition.
A pharmacist can answer most questions in this subcategory in a few minutes with access to a proper interaction database, and that access is the thing a forum does not have.
Reading it again, the caveat matters more than the finding.
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 is a small point and it changes the answer, which is an awkward combination.
Adding a data point of agreement rather than a data point.
On post #83 — agreed on the reasoning, with one qualification.
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.
I have left out the parts I could not verify.
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.
It reads as pedantry until the day it does not.
Post #87 and I disagree about the size of the effect, not about the direction.
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.
Worth checking against a second source before it gets quoted onward.