How to represent an IV medication with Additives

Looking for some help around compound medications - more specific - IV with additives. Just need a better understating how structure the medication resource for the medicaitonRequest resource.

First of all, in the case where a medication is being created by pharmacy, I would assume this would end up being a contained resource to the medicationRequest since this really isn’t a stocked pharmacy item?

My main concern is making sure to caputre the correct amount for the ordered medication.

Use Case - IV Medication Order with Additives

Physician orders an IV of 1000 mL Sodium Chloride with an additive. To be given to the patient twice a day at a rate of 125 mL/hour. This is a medication that the hospital pharmacy may mix before giving to nursing.

Base IV
• IV Sodium Chloride 0.9% - 1000mL in volume
The following Additive is mixed into the IV Bag -
• Potassium CI Injection 20 mEq/10 mL - 10 mL in volume

Total Volume = 1010 mL

Would the base IV bag exist at the medication resource level (parent) and the additives are listed at the ingredient level. Sort of like a parent - child layout. The initial “code” is your base medication and each “ingredient” is your additives.

Or for the medication resource, would all the medications be listed as an ingredient to the resource? Other words, you’d list out the “Form” which is an IV and each of the ingredients of that “form” would be listed - including the base medication.

For example -

{
“resourceType”: “medication”,
“form”: {
“coding”: [
{
“system”: “http://snomed.info/sct”,
“code”: “421410002”,
“display”: “Intravenous solution”
}
]
},
“ingredient”: [
{
“itemCodeableConcept”: {
“coding”: [
{
“system”: “http://hl7.org/fhir/sid/ndc”,
“code”: “00338-0125-04”,
“display”: “IV Sodium Chloride 0.9%”
}
]
},
“amount”: {
“numerator”: {
“value”: 1,
“system”: “http://unitsofmeasure.org”,
“code”: “IV Bag”
},
“denominator”: {
“value”: 1000,
“system”: “http://unitsofmeasure.org”,
“code”: “mL”
}
}
},
{
“itemCodeableConcept”: {
“coding”: [
{
“system”: “http://hl7.org/fhir/sid/ndc”,
“code”: “00338-0125-04”,
“display”: “Potassium CL Injection 20 mEq/10 mL”
}
]
},
“amount”: {
“numerator”: {
“value”: 20,
“system”: “http://unitsofmeasure.org”,
“code”: “mEq”
},
“denominator”: {
“value”: 10,
“system”: “http://unitsofmeasure.org”,
“code”: “mL”
}
}
}
]
}

I think you are mostly correct - I think that your quantities are slightly off.

I would do 1000ml / 1 Bag for the Sodium Chloride.

For the Potassium, since the drug code already implies the strength, then the quantity just needs to be 10ml / 1 Bag.

Thanks jduteau for the help!