Medication and primary active principle


My system represent medications with the list of active principles amounts and defining what is the primary active principle.

How this concept of primary active principle fits inside Medications resource?
Is there any known extension to represent it?

Looking from another angle, i cant even identify in SNOMED catalog the primary active principle.

Why is that?

Thanks in advance,

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Look at the Medication resource and the isActive flag on ingredient (so no need for extensions)

This probably isn’t the best place to ask about what SNOMED can and can’t do, What country are you implementing in? Depending on the country, SNOMED may not even be relevant for representing drugs.

Hi Lloyd,

Thanks for your quick response, we are implementing from Portugal.

I think I was not clear on the formulation of my question.

The problem is, consider the following medication that SULFAMETHOXAZOLE 400 mg/5 ml + TRIMETHOPRIM 80 mg/5 ml that has 2 active ingredients.

Additionally, we have a Medication Request for that medication where the dosage is defined in MG ex: 200 MG Every Day.

My question is, where can I say that the dosage refers to SULFAMETHOXAZOLE or TRIMETHOPRIM, should that information belong to the Medication Request or Medication? I can’t find where to put it.

It seems that something is missing because based on the example I gave it could be interpreted as:

How can FHIR help to disambiguate from option A) or B)?

Thanks in advance

If you’ve got a medication with multiple active ingredients, your dose should be expressed either in counts (if you’re dealing with discrete units such as Tylenol 3) - or in volume (e.g. 2.5mL/day if you wanted 200mg of the Sulfamethoxazole).

(That would be the safe/appropriate thing to do even if you were doing a paper prescription.)

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Thanks Lloyd, I agree with you that is the safest thing but normally doctors in hospitals would like to prescribe using MG as dose unit.

What do you think about extending medication to resource to identify the ingredient where dosage will refer to? Some drug databases refer to SULFAMETHOXAZOLE while other refer to TRIMETHOPRIM.


I think it wouldn’t be widely supported/recognized - and that when not supported/recognized it would be dangerous. I’d be surprised to find jurisdictions where professional bodies indicate that prescribing multi-active-ingredient medications based on the weight of only one ingredient is safe/appropriate. And if the professional bodies don’t indicate that it’s safe/appropriate, it’s not wise to try to force it into the standard merely on the basis of “some clinicians prefer to prescribe that way”.