Medication

Last updated: 2 Oct 2026

Introduction #

The Medication model represents a record of a medication that is being consumed by a patient, either now, in the past, or in the future. Medication records can represent both prescriptions and medication statements for a patient.

Basic usage #

To get a medication by identifier, use the get method on the Medication model manager:

from canvas_sdk.v1.data.medication import Medication

medication = Medication.objects.get(id="b80b1cdc-2e6a-4aca-90cc-ebc02e683f35")

If you have a patient object, the medications for a patient can be accessed with the medications attribute on a Patient object:

from canvas_sdk.v1.data.patient import Patient

patient = Patient.objects.get(id="1eed3ea2a8d546a1b681a2a45de1d790")
medications = patient.medications.all()

If you have a patient ID, you can get the medications for the patient with the for_patient method on the Medication model manager:

from canvas_sdk.v1.data.medication import Medication

patient_id = "1eed3ea2a8d546a1b681a2a45de1d790"
medication = Medication.objects.for_patient(patient_id)

Codings #

The codings for a medication can be accessed with the codings attribute on an Medication object:

from canvas_sdk.v1.data.medication import Medication
from logger import log

medication = Medication.objects.get(id="b80b1cdc-2e6a-4aca-90cc-ebc02e683f35")

for coding in medication.codings.all():
    log.info(f"system:  {coding.system}")
    log.info(f"code:    {coding.code}")
    log.info(f"display: {coding.display}")

Filtering #

Medications can be filtered by any attribute that exists on the model.

Filtering for medications is done with the filter method on the Medication model manager.

By attribute #

Specify an attribute with filter to filter by that attribute:

from canvas_sdk.v1.data.medication import Medication

medications = Medication.objects.filter(status="active")

By ValueSet #

See Value Sets for the library of built-in value sets and how to create your own.

Filtering by ValueSet works a little differently. The find method on the model manager is used to perform ValueSet filtering:

from canvas_sdk.v1.data.medication import Medication
from canvas_sdk.value_set.v2022.medication import AdhdMedications

medications = Medication.objects.find(AdhdMedications)

Latest sig #

The latest_sig property returns a medication’s most recent sig — its directions for use — as a string. It draws on three sources: the medication’s active prescriptions, its change medications that are not entered in error, and its medication statements. It returns the sig from whichever of those is most recent. Because latest_sig is a property computed in Python, it is read from each Medication object and is not available to a queryset .filter() or .order_by().

When both an active prescription and a change medication exist, the source whose note has the later date of service wins. Otherwise the sig comes from the first source that has one, in this order:

1. The latest prescription.
2. The latest change medication.
3. The latest medication statement.

The latest source is the one with the highest dbid. A prescription contributes its combined_sig (its sig text, plus a maximum daily dose when one is set); a change medication or medication statement contributes its sig text. When no source has a sig, latest_sig returns an empty string.

from canvas_sdk.v1.data.medication import Medication

medication = Medication.objects.get(id="b80b1cdc-2e6a-4aca-90cc-ebc02e683f35")
sig = medication.latest_sig  # "" when no source has a sig

Sig across many medications #

Reading latest_sig on each medication in a queryset issues a separate query per medication for the prescriptions, change medications, and medication statements latest_sig inspects. The with_latest_sig method prefetches those sources, so latest_sig resolves without a per-medication query:

from canvas_sdk.v1.data.medication import Medication

patient_id = "1eed3ea2a8d546a1b681a2a45de1d790"
medications = Medication.objects.for_patient(patient_id).with_latest_sig()

for medication in medications:
    sig = medication.latest_sig

Filtering to match the Patient Summary #

The Medications list in the Patient Summary section of the chart is not reproduced by filtering on status == "active" alone. Per Canvas, that list applies two exclusion layers before considering status:

1. Exclude uncommitted and entered-in-error records — a medication must have a non-null committer (it was finalized) and a null entered_in_error (no one flagged it as erroneous).
2. Filter by status — the list defaults to status == "active"; users can toggle to inactive or all.

The Medication queryset has both layers built in. committed() keeps records with a non-null committer and a null entered_in_error, and active() is committed() plus status == "active". To replicate the Patient Summary’s active medications:

from canvas_sdk.v1.data.medication import Medication

active_meds = Medication.objects.for_patient(patient_id).active()

For every medication the list can show (its “All” toggle, active plus inactive), use committed() without the status filter:

from canvas_sdk.v1.data.medication import Medication

all_visible_meds = Medication.objects.for_patient(patient_id).committed()

How status is computed #

Canvas sets a medication’s status from its command history; users do not set it directly. A medication is inactive when any of the following is true, and active otherwise:

• It has a committed stop medication event that has not been entered in error.
• Its prescription has a committed cancellation that has not been entered in error.
• A newer medication in the same chain of commands has replaced it, for example through an adjusted prescription.
• Its only commands are refill denials.
• It has no committed commands linked to it, apart from ones entered in error.

Canvas recomputes status, start_date, and end_date whenever a related command is created, committed, or entered in error. Related commands include medication statements, prescriptions, refills, adjustments, stop medication events, prescription cancellations, and eRx refill responses, and a change to a note’s date of service triggers it too.

The FHIR API is the exception. Creating a MedicationStatement through FHIR writes status and the effectivePeriod start and end straight onto the Medication record without recomputing them, and those values stay until a later command triggers a recomputation.

Attributes #

Medication #

Field Name	Type	Description
id	UUID
dbid	Integer
created	DateTime
modified	DateTime
patient	Patient
entered_in_error	CanvasUser
committer	CanvasUser
status	String
start_date	Date
end_date	Date
quantity_qualifier_description	String
clinical_quantity_description	String
potency_unit_code	String
national_drug_code	String
erx_quantity	String
codings	MedicationCoding[]
medication_statements	MedicationStatement[]
change_medications	ChangeMedication[]
stopmedicationevent_set	StopMedicationEvent[]
prescriptions	Prescription[]
previous_medications	Prescription[]
prescription_change_responses	PrescriptionChangeResponse[]
latest_sig	String (computed)	See Latest sig

MedicationCoding #

Field Name	Type
dbid	Integer
created	DateTime
modified	DateTime
system	String
version	String
code	String
display	String
user_selected	Boolean
medication	Medication