We have a use case in which we need to store the nutrition information of a medication that is mixed in the hospital. In https://jira.hl7.org/browse/FHIR-32278 you indicated that we could use the element MedicationKnowledge.drugCharacteristic to store the nutrition information.

Bellow we created an example (intravenous nutrition which is given as a medication infusion) of how we could model each mixed medication in FHIR.

Each mixed medication will create a new Medication instance as well as a new MedicationKnowledge instance as each mixed medication can follow a different mixing formula. Is correct the approach we are following? Is it ok if we create a new MedicationKnowledge for each individual mixed medication?

Usage: #example
Instance: TPNSolution234
InstanceOf: Medication

• identifier.id = "789708003" (THIS IS THE SNOMED CT CODE)
• code = http://hl7.org/fhir/sid/ndc#0409-4699-33 " Total parenteral nutrition agent (substance)"
• status = #active
• doseForm.coding.system = "http://snomed.info/sct"
• doseForm.coding.code = "385229008 "
• doseForm.coding.display = "Conventional release solution for infusion (dose form)"
  * volume: 1000ml (our extension)
• ingredient.item.concept.coding.system = "http://www.nlm.nih.gov/research/umls/rxnorm"
• ingredient.item.concept.coding.code = "346532000" (SNOMED CT)
• ingredient.item.concept.coding.display = " Intravenous nutrition - amino acids (product)
• ingredient.isActive = true
• ingredient.strengthRatio.numerator.value = 10
• ingredient.strengthRatio.numerator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.numerator.code = "gm"
• ingredient.strengthRatio.denominator.value = 100
• ingredient.strengthRatio.denominator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.denominator.code = "mL"
  * volume: 425ml (our extension)
• ingredient.item.concept.coding.system = "http://www.nlm.nih.gov/research/umls/rxnorm"
• ingredient.item.concept.coding.code = "346533005" (SNOMED CT)
• ingredient.item.concept.coding.display = " Intravenous nutrition - carbohydrate (product)
• ingredient.isActive = true
• ingredient.strengthRatio.numerator.value = 70
• ingredient.strengthRatio.numerator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.numerator.code = "gm"
• ingredient.strengthRatio.denominator.value = 100
• ingredient.strengthRatio.denominator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.denominator.code = "mL"
  * volume 450ml (our extension)
• ingredient.item.concept.coding.system = "http://www.nlm.nih.gov/research/umls/rxnorm"
• ingredient.item.concept.coding.code = "346535003" (SNOMED CT)
• ingredient.item.concept.coding.display = " Intravenous nutrition - fats (product)"
• ingredient.isActive = true
• ingredient.strengthRatio.numerator.value = 10
• ingredient.strengthRatio.numerator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.numerator.code = "gm"
• ingredient.strengthRatio.denominator.value = 100
• ingredient.strengthRatio.denominator.system = "http://unitsofmeasure.org"
• ingredient.strengthRatio.denominator.code = "mL"
  * volume 125ml (our extension)

Instance: medknowTPNSolution234
InstanceOf: MedicationKnowledge
Usage: #example

• identifier.id = 346532000" (SNOMED CT)
• code = TERMINOLOGY#AAAAAA " Total parenteral nutrition agent (substance)""
• status = #active
• associatedMedication = Reference (Medication/TPNSolution234)
• drugCharacteristic[+].type = #Fat
• drugCharacteristic[=].valueQuantity = 0.025gm/ml
• drugCharacteristic[+].type = #Calories
• drugCharacteristic[=].valueQuantity = 1.27 calories/ml
• drugCharacteristic[+].type = #Carbs
• drugCharacteristic[=].valueQuantity = 0.25gm/ml
• drugCharacteristic[+].type = #Protein
• drugCharacteristic[=].valueQuantity = 0.04gm/ml

**