Global Core Electronic Medicinal Product Information (ePI), published by HL7 International - Biomedical Research & Regulation Work Group. This guide is not an authorized publication; it is the continuous build for version 1.1.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/emedicinal-product-info/ and changes regularly. See the Directory of published versions

Build ePI Type 4

Implementing Structured Dose Syntax in ePI

This section provides guidance on implementing structured dose syntax within an ePI system using a custom FHIR R5 profile for the ClinicalUseDefinition resource, which incorporates the FHIR R5 Dosage structure. The implementation ensures interoperability across healthcare systems, supports both product-based and dose-based prescribing. These instructions were adapted from the NHS Dose Syntax Implementation Guide.

Overview

Structured dose syntax in ePI systems enables precise, machine-readable representation of dosage instructions for medicinal products. This is critical for:

• Interoperability: Sharing medication information between primary and secondary care settings (e.g., hospital admissions, discharge summaries).
• Patient Safety: Reducing errors in dose conversion between product-based and dose-based instructions.
• Patient Engagement: Supporting patient-facing applications with alerts for medication compliance.
• Automation: Enabling interactions with health systems (ePrescription, Electronic Healthcare records) or devices (mobile patient medication apps) to use structured data for accurate communications.

The FHIR R5 Dosage structure encodes dosage instructions, supporting simple and complex dosing scenarios. To integrate dosage instructions into the ePI, a custom profile for ClinicalUseDefinition is defined to include Dosage as a standard element, linked to a MedicinalProductDefinition for product-centric information.

note: Instructions for product manipulation or transformation (e.g., reconstitution) are Out-of-Scope.

Prerequisites

Before implementing structured dose syntax, ensure familiarity with:

• FHIR Dosage: Refer to Dosage for details on the structure.
• NHS Dose Syntax Implementation Guide: Refer to the NHS' guide for more detailed examples (NHS Dose Syntax).

Custom Profile for ClinicalUseDefinition

The ClinicalUseDefinition resource captures clinical particulars (e.g., indications, dosage recommendations) for a medicinal product. By default, it does not include a Dosage element. To address this, a custom FHIR R5 profile, EPIDosageClinicalUseDefinition, is defined to add a dosage element of type Dosage (0..*). This profile ensures dosage instructions are a first-class component of the ePI, improving clarity and interoperability compared to using extensions.

Key Components of FHIR R5 Dosage Structure

The FHIR R5 Dosage structure includes elements to describe dosage instructions comprehensively. Below are the key components relevant to ePI implementation, with their purpose and usage:

• sequence: Indicates the order of doses in a multi-step regimen (e.g., "take 2 tablets for 5 days, then 1 tablet for 5 days").
• text: A human-readable summary of the dosage instructions (e.g., "Take 1 tablet daily").
• additionalInstruction: Coded or free-text instructions (e.g., "Take with food").
• patientInstruction: Patient-friendly instructions (e.g., "Swallow with water").
• timing: Specifies when and how often the dose is taken, including frequency, period, and time of day.
• asNeeded: Indicates if the medication is taken as needed (boolean).
• asNeededFor: Specifies conditions for as-needed use (e.g., "for pain").
• site: The anatomical site of administration (e.g., "oral").
• route: The route of administration (e.g., "oral", "intravenous").
• method: The method of administration (e.g., "swallow", "inject").
• doseAndRate: The quantity or range of the dose (e.g., "500 mg") and rate (e.g., "10 ml/hour" for infusions).
• maxDosePerPeriod: The maximum dose allowed in a time period (e.g., "4 g per day").
• maxDosePerAdministration: The maximum dose per administration (e.g., "1 g per dose").
• maxDosePerLifetime: The maximum dose over a patient’s lifetime.

Implementation Steps

Follow these steps to integrate structured dose syntax into an ePI system using the custom EPIDosageClinicalUseDefinition profile:

1. Create the Resources
   • Use MedicinalProductDefinition to define the medicinal product (e.g., "Paracetamol 500mg tablets").
   • Use the profiled ClinicalUseDefinition to specify clinical particulars, including dosage instructions.
   • Ensure resources reference coded identifiers for the medicinal product (e.g., using SNOMED-CT or other standard terminologies).
2. Map Dosage Instructions
   • Simple Dosing: For common instructions (e.g., "Take 1 tablet daily"):
     • Set ClinicalUseDefinition.dosage.text to "Take 1 tablet daily".
     • Use dosage.timing to specify frequency: 1, period: 1, periodUnit: day.
     • Set dosage.doseAndRate.doseQuantity to value: 1, unit: tablet.
     • Set dosage.route to a coded value for "oral" (e.g., SNOMED-CT).
   • Complex Dosing: For multi-step or conditional regimens (e.g., "Take 2 tablets every 6 hours for 3 days, then 1 tablet daily"):
     • Use multiple dosage entries with sequence to indicate order.
     • Specify timing for each step (e.g., frequency: 4, period: 1, periodUnit: day for every 6 hours).
     • Include additionalInstruction for conditions like "Take with food" (use coded values where possible).
3. Support Product-Based and Dose-Based Instructions
   • Product-Based: Reference a specific medicinal product formulation in MedicinalProductDefinition. Include dosage.doseAndRate.doseQuantity with the product unit (e.g., "2 tablets").
   • Dose-Based: Reference a generic medicinal product and specify dosage.doseAndRate.doseQuantity with the active ingredient dose (e.g., "1000 mg").
   • Provide logic to map between product-based and dose-based instructions using standard terminologies.
4. Enhance Patient-Facing Features
   • Populate dosage.patientInstruction with clear, non-technical language (e.g., "Take one tablet every morning with breakfast").
   • Use dosage.timing to generate reminders in patient apps (e.g., schedule notifications for "08:00 AM daily").
   • Validate dosage.maxDosePerPeriod and dosage.maxDosePerAdministration to alert patients or clinicians about potential overdosing.
5. Ensure Interoperability
   • Validate the profiled ClinicalUseDefinition and Dosage structures against FHIR R5 using validation tools.
   • Use standard terminologies (e.g., SNOMED-CT) for dosage.route, dosage.site, dosage.method, and dosage.additionalInstruction.
   • Test data sharing between systems (e.g., manufacturer to healthcare provider) to confirm accurate interpretation of dosage instructions.
6. Handle Special Cases
   • As-Needed Medications: Set dosage.asNeeded to true and use dosage.asNeededFor for conditions (e.g., "pain").
   • Infusions: Use dosage.doseAndRate.rateQuantity for continuous administration (e.g., "10 ml/hour").
   • Variable Dosing: Use doseRange instead of doseQuantity for flexible doses (e.g., "1-2 tablets").

Examples

Below are examples of a MedicinalProductDefinition and a profiled ClinicalUseDefinition with an extension (as an interim approach) for "Paracetamol 500mg, take 2 tablets every 6 hours for 3 days, maximum 8 tablets per day". Note that in the custom profile, the dosage element would replace the extension, but the extension is included here as an interim example.

MedicinalProductDefinition

{
  "resourceType": "MedicinalProductDefinition",
  "id": "paracetamol-500mg",
  "name": [
    {
      "productName": "Paracetamol 500mg Tablets"
    }
  ],
  "clinicalUseIssue": [
    {
      "reference": "ClinicalUseDefinition/paracetamol-dosage"
    }
  ]
}

ClinicalUseDefinition (with Extension)

{
  "resourceType": "ClinicalUseDefinition",
  "id": "paracetamol-dosage",
  "meta": {
    "profile": [
      "http://example.org/fhir/StructureDefinition/EPIDosageClinicalUseDefinition"
    ]
  },
  "type": "indication",
  "subject": [
    {
      "reference": "MedicinalProductDefinition/paracetamol-500mg"
    }
  ],
  "indication": {
    "diseaseSymptomProcedure": {
      "coding": [
        {
          "system": "http://snomed.info/sct",
          "code": "387517004",
          "display": "Pain"
        }
      ]
    }
  },
  "extension": [
    {
      "url": "http://hl7.org/fhir/StructureDefinition/recommendedDosage",
      "valueDosage": {
        "sequence": 1,
        "text": "Take 2 tablets every 6 hours for 3 days",
        "patientInstruction": "Take 2 tablets every 6 hours with water, do not exceed 8 tablets in 24 hours",
        "timing": {
          "repeat": {
            "frequency": 4,
            "period": 1,
            "periodUnit": "d",
            "duration": 3,
            "durationUnit": "d"
          }
        },
        "route": {
          "coding": [
            {
              "system": "http://snomed.info/sct",
              "code": "26643006",
              "display": "Oral"
            }
          ]
        },
        "doseAndRate": [
          {
            "doseQuantity": {
              "value": 2,
              "unit": "tablet",
              "system": "http://snomed.info/sct",
              "code": "428673006"
            }
          }
        ],
        "maxDosePerPeriod": {
          "numerator": {
            "value": 8,
            "unit": "tablet",
            "system": "http://snomed.info/sct",
            "code": "428673006"
          },
          "denominator": {
            "value": 1,
            "unit": "day",
            "system": "http://unitsofmeasure.org",
            "code": "d"
          }
        }
      }
    }
  ]
}