We have a use case in which we record both strength and amount of a Medication ingredient (solutions mixed in the hospital). Here is an example:
400 mg of Dopamine added to an infusion of Normal Saline, resulting in a concentration of 1600 mcg/ml.
Strength: 1600 mcg/ml
Amount of the ingredient in the solution: 400 mg

We would like to know how we could record this information in FHIR Medication.
We can only record the quantity OR the strength (cardinality of strength is 0..1). How to represent both simultaneously?

Medication.ingredient.item = Reference (Dopamine)

Medication.ingredient.strengthQuantity = 400mg
OR
Medication.ingredient.strengthRatio = 1600 mcg/ml

This ticket is related to https://jira.hl7.org/browse/FHIR-34187