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.

Element: maxDosePer

Dosing maxDosePerPeriod, maxDosePerAdministration and 'maxDosePerLifetime' instructions

Dosage.maxDosePerPeriod

Used to define a maxiumum dose over a given time period.

An example would be a Sumatriptan 6mg injection which can be repeated after an hour but not again over a 24 hour period. The maxDosePerPeriod is defined as 12mg/24hours.

The maxDosePerPeriod is defined for each dosage instruction. For a multi-sequence instruction it would therefore be possible to define different maximum dosing periods within different sequences of the complete instruction.

A real-world example of where this would be required has not yet been identified.

Maximum dose per period of 12mg/24 hour

<maxDosePerPeriod>
    <numerator>
        <value value="12"/>
        <unit value="milligram"/>
        <system value="http://unitsofmeasure.org"/>
        <code value="mg"/>
    </numerator>
    <denominator>
        <value value="24"/>
        <unit value="hour"/>
        <system value="http://unitsofmeasure.org"/>
        <code value="h"/>
    </denominator>
</maxDosePerPeriod>

Dosage.maxDosePerAdministration

Used to define a maximum dose for a single administration.

An example would be Anagrelide for which a single dose should not exceed 2.5 mg. The maxDosePerAdministration is defined as 2.5mg.

In many scenarios it is expected that the dosage.doseRange would be used instead of maxDosePerAdministration.

The maxDosePerAdministration is defined for each dosage instruction. For a multi-sequence instruction it would therefore be possible to define different maximum dose administrations within different sequences of the complete instruction.

A real-world example of where this would be required has not yet been identified.

Maximum dose per administration of 2.5mg

<maxDosePerAdministration>
    <value value="2.5"/>
    <unit value="milligram"/>
    <system value="http://unitsofmeasure.org"/>
    <code value="mg"/>
</maxDosePerAdministration>

Dosage.maxDosePerLifetime

Used to define the maximum cumulative dose over the lifetime of a patient.

An example would be Daunorubicin which may have a maximum cumulative dose of 600mg/m2 (based on the size of the patient). The maxDosePerLifetime is defined as 600 mg/m2.

The maxDosePerLifetime can be defined for each dosage instruction; which, for a multi-sequence instruction is illogical, as any maxDosePerLifetime is equally applicable to all dosage sequence that relate to the single medication coded concept.

Note: If a maxDosePerLifetime statement is required with a multi-sequence instruction, it is recommended to define it within the last / final sequence to ensure that the information is presented at the end of a the complete instruction, rather than th middle which could be overlooked.

Maximum dose over lifetime of the patient of 600 mg/m2

<maxDosePerLifetime>
    <value value="600"/>
    <unit value="milligram per square metre"/>
    <system value="http://unitsofmeasure.org"/>
    <code value="mg/m2"/>
</maxDosePerLifetime>
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