Implementation Guide
ePA Medication Service
Version 1.2.0-ballot.2 - draft

## Extension: DrugCategoryExtension - Detailed Descriptions

Draft as of 2025-09-02

Definitions for the drug-category-extension extension.

- Key Elements Table
- Differential Elements Table
- Snapshot Elements Table

Guidance on how to interpret the contents of this table can be foundhere

0. Extension
Definition | Extension for indicating the medication category. Optional Extension Element - found in all resources.
Short | ExtensionOptional Extensions Element
Control | 0..* This element is affected by the following invariants: ele-1
Is Modifier | false
Invariants | ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
2. Extension.extension
Definition | An Extension May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short | ExtensionAdditional content defined by implementations
Comments | There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control | 0..0* This element is affected by the following invariants: ele-1
Type | Extension
Is Modifier | false
Summary | false
Alternate Names | extensions, user content
Invariants | ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing | This element introduces a set of slices on `Extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
4. Extension.url
Definition | Source of the definition for the extension code - a logical name or a URL.
Short | identifies the meaning of the extension
Comments | The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control | 1..1
Type | uri
XML Format | In the XML format, this property is represented as an attribute.
Fixed Value | `https://gematik.de/fhir/epa-medication/StructureDefinition/drug-category-extension`
6. Extension.value[x]
Definition | Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short | Value of extension
Control | 10..1 This element is affected by the following invariants: ele-1
Binding | The codes SHALL be taken from For codes, see TI Drug Category ValueSet (required to `https://gematik.de/fhir/terminology/ValueSet/ti-drug-category-vs` )
Type | Coding, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, SampledData, id, positiveInt, Distance, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, CodeableConcept, ParameterDefinition, dateTime, code, string, Contributor, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, Signature, unsignedInt, time
[x] Note | SeeChoice of Data Typesfor further information about how to use [x]
Is Modifier | false
Invariants | ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
8. Extension.value[x].code
Definition | Drug Category A symbol in syntax defined by the system. The symbol may be a predefined code or an expression in a syntax defined by the coding system (e.g. post-coordination).
Short | CategorySymbol in syntax defined by the system
Control | 0..1
Type | code
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Requirements | Need to refer to a particular code in the system.
Invariants | ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))

Guidance on how to interpret the contents of this table can be foundhere

0. Extension
Definition | Extension for indicating the medication category.
2. Extension.extension
Control | 0..0
4. Extension.url
Fixed Value | `https://gematik.de/fhir/epa-medication/StructureDefinition/drug-category-extension`
6. Extension.value[x]
Control | 1..?
Binding | The codes SHALL be taken from TI Drug Category ValueSet (required to `https://gematik.de/fhir/terminology/ValueSet/ti-drug-category-vs` )
Type | Coding, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, SampledData, id, positiveInt, Distance, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, CodeableConcept, ParameterDefinition, dateTime, code, string, Contributor, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, Signature, unsignedInt, time
[x] Note | SeeChoice of Data Typesfor further information about how to use [x]
8. Extension.value[x].code
Definition | Drug Category
Short | Category

Guidance on how to interpret the contents of this table can be foundhere

0. Extension
Definition | Extension for indicating the medication category.
Short | Extension
Control | 0..* This element is affected by the following invariants: ele-1
Is Modifier | false
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
2. Extension.id
Definition | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short | Unique id for inter-element referencing
Control | 0..1
Type | string
Is Modifier | false
XML Format | In the XML format, this property is represented as an attribute.
Summary | false
4. Extension.extension
Definition | An Extension
Short | Extension
Control | 0..0
Type | Extension
Is Modifier | false
Summary | false
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing | This element introduces a set of slices on `Extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
6. Extension.url
Definition | Source of the definition for the extension code - a logical name or a URL.
Short | identifies the meaning of the extension
Comments | The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control | 1..1
Type | uri
XML Format | In the XML format, this property is represented as an attribute.
Fixed Value | `https://gematik.de/fhir/epa-medication/StructureDefinition/drug-category-extension`
8. Extension.value[x]
Definition | Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short | Value of extension
Control | 1..1 This element is affected by the following invariants: ele-1
Binding | The codes SHALL be taken from TI Drug Category ValueSet (required to `https://gematik.de/fhir/terminology/ValueSet/ti-drug-category-vs` )
Type | Coding
[x] Note | SeeChoice of Data Typesfor further information about how to use [x]
Is Modifier | false
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
10. Extension.value[x].id
Definition | Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short | Unique id for inter-element referencing
Control | 0..1
Type | string
Is Modifier | false
XML Format | In the XML format, this property is represented as an attribute.
Summary | false
12. Extension.value[x].extension
Definition | May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short | Additional content defined by implementations
Comments | There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control | 0..*
Type | Extension
Is Modifier | false
Summary | false
Alternate Names | extensions, user content
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing | This element introduces a set of slices on `Extension.value[x].extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
14. Extension.value[x].system
Definition | The identification of the code system that defines the meaning of the symbol in the code.
Short | Identity of the terminology system
Comments | The URI may be an OID (urn:oid:...) or a UUID (urn:uuid:...). OIDs and UUIDs SHALL be references to the HL7 OID registry. Otherwise, the URI should come from HL7's list of FHIR defined special URIs or it should reference to some definition that establishes the system clearly and unambiguously.
Control | 0..1
Type | uri
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Requirements | Need to be unambiguous about the source of the definition of the symbol.
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
16. Extension.value[x].version
Definition | The version of the code system which was used when choosing this code. Note that a well-maintained code system does not need the version reported, because the meaning of codes is consistent across versions. However this cannot consistently be assured, and when the meaning is not guaranteed to be consistent, the version SHOULD be exchanged.
Short | Version of the system - if relevant
Comments | Where the terminology does not clearly define what string should be used to identify code system versions, the recommendation is to use the date (expressed in FHIR date format) on which that version was officially published as the version date.
Note | This is a business version Id, not a resource version Id (see discussion)
Control | 0..1
Type | string
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
18. Extension.value[x].code
Definition | Drug Category
Short | Category
Control | 0..1
Type | code
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Requirements | Need to refer to a particular code in the system.
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
20. Extension.value[x].display
Definition | A representation of the meaning of the code in the system, following the rules of the system.
Short | Representation defined by the system
Comments | Note that FHIR strings SHALL NOT exceed 1MB in size
Control | 0..1
Type | string
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Requirements | Need to be able to carry a human-readable meaning of the code for readers that do not know the system.
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
22. Extension.value[x].userSelected
Definition | Indicates that this coding was chosen by a user directly - e.g. off a pick list of available items (codes or displays).
Short | If this coding was chosen directly by the user
Comments | Amongst a set of alternatives, a directly chosen code is the most appropriate starting point for new translations. There is some ambiguity about what exactly 'directly chosen' implies, and trading partner agreement may be needed to clarify the use of this element and its consequences more completely.
Control | 0..1
Type | boolean
Is Modifier | false
Primitive Value | This primitive element may be present, or absent, or replaced by an extension
Summary | true
Requirements | This has been identified as a clinical safety criterium - that this exact system/code pair was chosen explicitly, rather than inferred by the system based on some rules or language processing.
Invariants | ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)