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.
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Practice · Interactions · continued
Second pass at: Metformin co-administration and additive GI effects posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
t.batista, post #22: Metformin co-administration is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which one is being asked for. Go to post
Posting my Metformin co-administration numbers with the method attached so they can be discounted properly. Uncontrolled, unblinded, and collected by someone who wanted a particular answer.
Metformin co-administration is a good example of a question where the honest answer is boring and the interesting answers are unsupported. I would go with boring.
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DOdendaal, post #14: Narrowing post #11, because the general version has more than one answer. 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. Go to post
On post #33 — agreed on the reasoning, with one qualification.
SGLT2 inhibitors: frequently co-administered and relevant to renal and cardiovascular discussion, not to interactions. There is no pharmacokinetic interaction of concern.
I have no interest in any supplier named above.
r.chukwu, post #28: Post #26 describes the usual case. This is about the unusual one. 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. The step people skip is the one I have spelled out. Go to post
I read post #37 twice before replying, because I had assumed the opposite.
Where I would push back on the Metformin co-administration consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
b.jankowiak, post #20: This follows post #19 rather than contradicting it. 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. Go to post
I came in to disagree and I am leaving without a disagreement.
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.
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I read post #41 twice before replying, because I had assumed the opposite.
Metformin: commonly co-administered and relevant to gastrointestinal tolerability. Gastrointestinal side effects can overlap and additive. Taking them separately or adjusting one if tolerability is poor are reasonable approaches.
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l.wikstrom, post #42: I read post #41 twice before replying, because I had assumed the opposite. Metformin: commonly co-administered and relevant to gastrointestinal tolerability. Gastrointestinal side effects can overlap and additive. Taking them separately or adjusting one if tolerability is poor are reasonable approaches. Go to post
Taking post #42 at face value and following it one step further.
A note on how Metformin co-administration gets discussed rather than on Metformin co-administration itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often.
a.vukovic, post #10: Distinguishing three things in the Metformin co-administration discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both. Go to post
Worth stating the null on Metformin co-administration before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.
Narrowing post #42, because the general version has more than one answer.
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.
That is what I would do. It may not be what is correct.
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Everything in post #44 holds. The case it does not cover is the one I have.
The arithmetic on Metformin co-administration is the easy part and it is where the errors are, which is an uncomfortable combination. Show your working and someone will catch it.
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sterile_file, post #16: Taking post #15 at face value and following it one step further. I changed my mind about Metformin co-administration after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens. Go to post
Reading back through, this was answered upthread and I missed it. My fault.
The arithmetic in post #46 is right; the assumption feeding it is the part to check.
Offering a way to settle Metformin co-administration rather than another opinion about it. Two measurements, taken the same way, a fortnight apart. If the difference is within the noise, the question was not answerable at this precision.
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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.
That has held every time I have looked, which is not the same as always.
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sterile_file, post #16: Taking post #15 at face value and following it one step further. I changed my mind about Metformin co-administration after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens. Go to post
Following, with nothing to contribute beyond having asked the same thing elsewhere.
Collapsed as off-topic by two members at trust level 3 or above
Everything in post #52 holds. The case it does not cover is the one I have.
Answering the Metformin co-administration 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.
Narrowing post #54, because the general version has more than one answer.
Food interactions: most interactions are absorption interactions. Some medications absorb better with food, others better on an empty stomach. With an incretin agonist that already slows gastric emptying, food effects interact with the drug effect as well.
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I would put moderate confidence on the mainstream reading of Metformin co-administration and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.
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The question underneath Metformin co-administration is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
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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.
A guess, clearly labelled as one.
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