Hi Linda,
@mcordell and I discussed this yesterday, sorry we didn’t get back to you sooner.
AMT currently uses has active ingredient = inert substance. This pattern comes from AMT v3, which inherited it from v2, and so on.
Here’s some examples, first the "clinical drug” level concept
and a “real clinical drug” level concept
Personally, I have never been comfortable with this modelling. “Has active ingredient = inert substance” feels like an oxymoron, although it depends on how you define “active” and “inert”. Likewise, concepts like “Loette (inert substance) tablet” with a non-zero count of active ingredients seem logically inconsistent.
My preference would be to avoid using has active ingredient (or any subproperty) altogether for inert products. Nothing in these products is intended to be active by definition. A simple “count of active ingredient = 0” is accurate, and in my view sufficient to define the concept. If I could redesign this part of AMT, that is the approach I would take.
That said, the current AMT implementation does not cause any functional problems that I am aware of. AMT has used this pattern for nearly twenty years, and there has been no push from stakeholders to change it. If I tried to convince vendors to adopt a revised model, I doubt I could demonstrate enough practical benefit to justify the cost and consultation effort. So although the current pattern is not ideal, changing it would be hard to justify.
On diluents, I would not model “sterile water” or “sodium chloride” as active ingredients, even though AMT sometimes does so. These substances do not meet the definition of active ingredient:
The clinically relevant part or whole of the substance that is intended to have a therapeutic action on or within the body. It excludes esters, salts or other non-covalent derivatives (such as a complex, chelate etc.), but may include secondary modifications.
AMT mostly uses the same pattern as the inert tablets for diluents, with has active ingredient = inert substance, and usually does not specify the actual excipients because AMT does not model excipients for active products either.
But in some cases like this multi chamber drug, it does model the ingredient in the diluent chamber
I find this awkward. Sodium chloride in a diluent does not have a therapeutic action. It is a functional ingredient, which is a subtype of excipient. In this case it is a tonicity adjuster that supports safe and comfortable administration but does not contribute to the therapeutic effect.
I am not saying we should not model these ingredients. I am saying they are not active ingredients according to the definition. Ideally, we would have a separate branch under has ingredient for inactive ingredients, with the option to further specify their functional roles if useful.
Again, this is something I would change about AMT if the costs and benefits made sense, but at present they do not.
If I were to remodel diluents, I would treat them the same way as inert tablets: count of active ingredient = 0 with no has active ingredient relationship. I would only explicitly model diluent ingredients where clinically necessary or useful, and I would represent them using a separate subproperty under has ingredient, not under has active ingredient.
Those are my thoughts on what I would do different, but as I said I would have a hard time selling that change in and of itself - unless I’m missing some existing problems or benefits.
I hope that’s useful,
Dion
