Dose syntax implementation guidance for FHIR STU3

This guidance is under active development by NHS Digital and content may be added or updated on a regular basis.

3. STU3 Limitation - Cyclical prescribing - Defining a period of time where medication should not be taken

Workaround: Use a free-text `Dosage.additionalInstruction`.

The example given for the current limitation for defining a maximum dose per course also includes an instruction for a period of time where medication should not be taken. This is not directly supported within the STU3 Dosage structure.

Another clinical example would be for a Lidocaine medicated plaster. A typical written dosage instruction would be;

Apply 2 patches once daily to the affected area for up to 12 hours, followed by a 12-hour plaster-free period; to be applied to intact, dry, non-hairy, non-irritated skin.

The FHIR STU3 Dosage structure can describe all the above except for the clause “followed by a 12-hour plaster-free period”.

In a dose-based instruction this would needs to be expressed as free-text within a Dosage.additionalInstruction.

An example of a sequencial instruction can be found below.

Microgynon 30 tablets (Bayer Plc), 1 tablet, ONCE a DAY, oral, for 21 days, subsequent courses repeated after 7-day tablet-free interval

Product-based AMP prescription using additional instructions to convery pill free interval. 
<MedicationRequest xmlns="http://hl7.org/fhir">
    <id value="d4b05cfb-d444-4490-824a-67c55596c610" />
    <contained>
        <Medication>
            <id value="med1" />
            <code>
                <coding>
                    <system value="http://snomed.info/sct" />
                    <code value="42111000001107" />
                    <display value="Microgynon 30 tablets (Bayer Plc)" />
                </coding>
            </code>
        </Medication>
    </contained>
    <status value="active" />
    <intent value="order" />
    <medicationReference>
        <reference value="#med1" />
    </medicationReference>
    <subject>
        <identifier>
            <system value="https://fhir.nhs.uk/Id/nhs-number" />
            <value value="9999999999" />
        </identifier>
    </subject>
    <dosageInstruction>
        <additionalInstruction>
            <text value="subsequent courses repeated after 7-day tablet-free interval" />
        </additionalInstruction>
        <timing>
            <repeat>
                <boundsDuration>
                    <value value="21" />
                    <unit value="day" />
                    <system value="http://unitsofmeasure.org" />
                    <code value="d" />
                </boundsDuration>
                <frequency value="1" />
                <period value="1" />
                <periodUnit value="d" />
            </repeat>
        </timing>
        <route>
            <coding>
                <system value="http://snomed.info/sct" />
                <code value="26643006" />
                <display value="oral" />
            </coding>
        </route>
        <doseQuantity>
            <value value="1" />
            <unit value="tablet" />
            <system value="http://snomed.info/sct" />
            <code value="428673006" />
        </doseQuantity>
    </dosageInstruction>
</MedicationRequest>

{
    "resourceType": "MedicationRequest",
    "id": "d4b05cfb-d444-4490-824a-67c55596c610",
    "contained":  [
        {
            "resourceType": "Medication",
            "id": "med1",
            "code": {
                "coding":  [
                    {
                        "system": "http://snomed.info/sct",
                        "code": "42111000001107",
                        "display": "Microgynon 30 tablets (Bayer Plc)"
                    }
                ]
            }
        }
    ],
    "status": "active",
    "intent": "order",
    "medicationReference": {
        "reference": "#med1"
    },
    "subject": {
        "identifier": {
            "system": "https://fhir.nhs.uk/Id/nhs-number",
            "value": "9999999999"
        }
    },
    "dosageInstruction":  [
        {
            "additionalInstruction":  [
                {
                    "text": "subsequent courses repeated after 7-day tablet-free interval"
                }
            ],
            "timing": {
                "repeat": {
                    "boundsDuration": {
                        "value": 21,
                        "unit": "day",
                        "system": "http://unitsofmeasure.org",
                        "code": "d"
                    },
                    "frequency": 1,
                    "period": 1,
                    "periodUnit": "d"
                }
            },
            "route": {
                "coding":  [
                    {
                        "system": "http://snomed.info/sct",
                        "code": "26643006",
                        "display": "oral"
                    }
                ]
            },
            "doseQuantity": {
                "value": 1,
                "unit": "tablet",
                "system": "http://snomed.info/sct",
                "code": "428673006"
            }
        }
    ]
}
MedicationRequest.id[0]d4b05cfb-d444-4490-824a-67c55596c610
MedicationRequest.contained[0].id[0]med1
MedicationRequest.contained[0].code[0].coding[0].system[0]http://snomed.info/sct
MedicationRequest.contained[0].code[0].coding[0].code[0]42111000001107
MedicationRequest.contained[0].code[0].coding[0].display[0]Microgynon 30 tablets (Bayer Plc)
MedicationRequest.status[0]active
MedicationRequest.intent[0]order
MedicationRequest.medication[0].reference[0]#med1
MedicationRequest.subject[0].identifier[0].system[0]https://fhir.nhs.uk/Id/nhs-number
MedicationRequest.subject[0].identifier[0].value[0]9999999999
MedicationRequest.dosageInstruction[0].additionalInstruction[0].text[0]subsequent courses repeated after 7-day tablet-free interval
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].bounds[0].value[0]21
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].bounds[0].unit[0]day
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].bounds[0].system[0]http://unitsofmeasure.org
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].bounds[0].code[0]d
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].frequency[0]1
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].period[0]1
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].periodUnit[0]d
MedicationRequest.dosageInstruction[0].route[0].coding[0].system[0]http://snomed.info/sct
MedicationRequest.dosageInstruction[0].route[0].coding[0].code[0]26643006
MedicationRequest.dosageInstruction[0].route[0].coding[0].display[0]oral
MedicationRequest.dosageInstruction[0].dose[0].value[0]1
MedicationRequest.dosageInstruction[0].dose[0].unit[0]tablet
MedicationRequest.dosageInstruction[0].dose[0].system[0]http://snomed.info/sct
MedicationRequest.dosageInstruction[0].dose[0].code[0]428673006
MedicationRequest
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