HL7 RRE messages acknowledge or respond to an encoded pharmacy order. An RRE message is sent from the pharmacy information system (PIS) back to the ordering application (such as an EHR) to confirm that the pharmacist has reviewed, validated, and encoded a medication order, updating it with pharmacy-specific details (like exact NDC codes, formulation, and dispensing directions). This page explains what an RRE message represents, the trigger event that carries it, every segment the message can contain and what each one holds, and how an RRE response relates to FHIR. Sample content is constructed for illustration with fictional identifiers.
What an RRE message represents
An RRE message — RRE stands for Pharmacy Encoded Order Acknowledgement — communicates the pharmacy's final verification and encoding of a prescription. While the raw order uses the RXO segment, the RRE message echoes the PIS-encoded order using the RXE segment (Pharmacy Encoded Order). The RXE segment carries the specific dispensing details: PIS medication codes, exact dosage form, package size, pharmacist-defined timing schedules, and patient instructions.
The sender is the pharmacy information system (PIS), and the receiver is the EHR or clinical application that originally submitted the pharmacy order (often as an OMP or RDE message). RRE provides clinical confirmation that the pharmacist has completed their review and the medication is active in the pharmacy's dispensing queue.
When an RRE message is sent
An RRE message is sent asynchronously after a pharmacist reviews and verifies a medication order in the PIS. It fires when the pharmacist clicks "verify," which encodes the raw order into a specific dispensing product, or when the pharmacy system rejects the order due to clinical validation errors.
Trigger event
The RRE message type carries a single trigger event:
RRE^O12– Pharmacy encoded order acknowledgement message.
The receiving application matches the response to the original order using the placer order number in ORC-2 and the message control ID echoed in MSA-2.
Integration topology
The diagram shows the pharmacy system returning an encoded order response through the integration engine to the ordering EHR.
{{diagram: pharmacy system → RRE message → integration engine → clinical system (EHR)}}
Typical senders: pharmacy information system (PIS), pharmacy dispensing application, inpatient pharmacy database.
Typical receivers: EHR, computerized physician order entry (CPOE) terminal, nursing documentation software.
Direction: response in a request-response pattern — the PIS acknowledges and encodes the clinician's medication order.
Segments in an RRE message
The RRE_O12 message opens with a header block (MSH, MSA, and optional ERR segments) followed by optional patient/visit context and one or more repeating ORDER groups. Cardinality follows HL7 notation: [X] optional, {X} repeating, [{X}] optional and repeating; a bare code is required. Each segment code links to its canonical field-by-field reference.
| Segment | Description |
|---|---|
MSH | Message Header. Opens every RRE message. It names the sending and receiving applications, stamps the creation time, declares the trigger event in MSH-9 (RRE^O12), carries the message control id in MSH-10, and pins the HL7 version. |
MSA | Message Acknowledgement. Required. Echoes the original message control id in MSA-2 and carries the acknowledgement code (e.g., AA accepted, AE error). |
[{ERR}] | Error. Details validation or application errors encountered when processing the medication order. Optional and repeating. |
[{NTE}] | Notes and Comments. Header-level comments or text notes. Optional and repeating. |
[PID] | Patient Identification. Patient associated with the pharmacy order. Optional. |
[PV1] | Patient Visit. Encounter details related to the patient. Optional. |
ORC | Common Order. Opens each ORDER group. It carries the order status, the placer order number, and the filler order number. Required within each repeating order group. |
[{TQ1}] | Timing/Quantity. Detailed frequency and administration schedule for the medication. Optional and repeating. |
RXE | Pharmacy Encoded Order. Required. Carries the PIS-encoded medication name/code, dose, units, form, and pharmacy instructions. |
[{RXR}] | Pharmacy Route. The route of administration (e.g., oral, intravenous). Optional and repeating. |
[{RXC}] | Pharmacy Component. Details of drug components or ingredients for compound orders. Optional and repeating. |
[{NTE}] | Notes and Comments (Line). Notes or pharmacist instructions for this specific medication line. Optional. |
[ ] = optional, { } = repeating
Sample RRE message
Note. Constructed for illustration. Medication codes, order numbers, and patient identifiers are fictional.
MSH|^~&|PHARMSYS|MERCY|EHRSYS|MERCY|20260604090000||RRE^O12^RRE_O12|MSG00048|P|2.5.1
MSA|AA|MSG00047
PID|1||MR98765^^^MERCY^MR||SMITH^PATRICIA^A||19720315|F
ORC|OK|REQ20260604-003^EHRSYS|FIL20260604-003^PHARMSYS
RXE|1^QD|500^Amoxicillin^L|500|mg|capsule|||||||||||
RXR|PO^Oral^HL70162
NTE|1||Pharmacist verified. NDC 0093-3109-05 mapped for dispensing.
What this sample shows
The RRE^O12 in MSH-9 marks a pharmacy encoded order response. MSA carries acknowledgement code AA (Application Accept) and acknowledges the original request control ID MSG00047. PID associates the response with patient MR98765. ORC carries order status OK (Order Accepted), links to placer order number REQ20260604-003, and supplies the pharmacy filler order number FIL20260604-003. The RXE segment carries the pharmacist-encoded order: dosage frequency code QD (Daily) in RXE-1, medication Amoxicillin in RXE-2, dose 500 mg in RXE-3 and RXE-4, form capsule in RXE-5. RXR specifies route PO (Oral). The NTE notes that the item has been verified and mapped to a specific NDC barcode.
Working with RRE messages
Matching and Verification
When an RRE response is received, the ordering system correlates MSA-2 with the outbound request. The placer order number in ORC-2 is used to match individual lines. This correlation is essential for clinical staff to verify that the pharmacy has reviewed and verified the order before administration begins.
Tracking Pharmacist Modifications
Pharmacists frequently modify the medication order during the encoding process (for example, substituting a brand name drug for a generic equivalent, or selecting a specific package form). Clinical systems must compare the PIS-encoded fields in the RXE segment against their original request details to ensure that nursing documentation and drug-administration records match the actual medication being dispensed.
Vendor variance. Different pharmacy systems use different coding systems in the
RXEsegment. Some systems return standard NDC codes inRXE-2, while others use hospital-specific formulary codes. Ensure your integration client parses both coding tables to support inventory tracking.
FHIR equivalent
A pharmacy encoded order response maps conceptually to status changes on the FHIR MedicationRequest resource, representing updates to the status field (e.g. from draft to active or completed).
The HL7 v2-to-FHIR Implementation Guide publishes no message map for RRE_O12 and no ConceptMap for the RXE segment. Consequently, any FHIR translation must be mapped manually, using MSA-2 and ORC-2 to locate the existing MedicationRequest resource and updating its status or adding pharmacy filler identifiers as identifier elements.
Common pitfalls
Pitfall. Assuming the order is active without checking
ORC-5orMSA-1. Presuming pharmacy acceptance on an error or rejection response can lead to clinical staff attempting to administer medication that was never dispensed.
Pitfall. Overlooking pharmacist modifications. Ignoring updates in the echoed
RXEsegment can result in the EHR displaying the doctor's original requested dose while the pharmacy is dispensing a modified dose.
How Vorro handles RRE messages
Vorro ingests RRE responses over MLLP, validates the application acknowledgement code in MSA, and correlates each response to its originating request. Vorro updates the status of the medication line items in the ordering EHR based on ORC-5 (Order Status) and passes through the pharmacy filler order number from ORC-3. Where a FHIR destination is configured, Vorro updates the corresponding MedicationRequest resource state manually, since the HL7 v2-to-FHIR guide provides no published map for this message.
Related messages
- RDE — the pharmacy encoded order message.
- RDS — the pharmacy dispense message.
- RAS — the pharmacy administration message.
