Metformin co-administration and additive GI effects Writing it up because I had to work it out twice and would rather nobody else did.
Trying to work out what would count as evidence on metformin co-administration, before collecting any. This is the part I usually skip and it is the part that makes the rest useful.
If two explanations predict the same observation, observing it does not help. So: what observation would separate them?
Narrowing the opening post, because the general version has more than one answer.
An observation about metformin co-administration that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
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.
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.
The mechanism is plausible, which is not the same as established.
The arithmetic in post #5 is right; the assumption feeding it is the part to check.
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.
My understanding of metformin co-administration is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it.
Post #5 describes the usual case. This is about the unusual one.
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.
Filing a mild objection to the consensus on metformin co-administration. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit.
Building on post #10 rather than restating 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.
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.
Two people in this thread mean different things by metformin co-administration and are disagreeing about the definition while believing they are disagreeing about the facts. Worth pausing to define it.
Taking post #14 at face value and following it one step further.
The version of metformin co-administration that circulates here is a simplification of a simplification. It is not wrong, but it has lost the conditions under which it holds, and those conditions are where the interesting cases live.
Post #16 and I disagree about the size of the effect, not about the direction.
SGLT2 inhibitors: frequently co-administered and relevant to renal and cardiovascular discussion, not to interactions. There is no pharmacokinetic interaction of concern.
That is a cleaner way of putting what I was circling around.
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.
This follows post #21 rather than contradicting it.
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.
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.
The honest answer is that it depends, and here is what it depends on.
Thank you for the correction. I would rather find out here than later.
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.
On metformin co-administration the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that.