Dose syntax implementation guidance for FHIR STU3

Timing Elements: when, offset, dayOfWeek, timeOfDay, event and code

A dosage instruction can be tied to the specific days, dates and times, plus life events related to eating or sleeping.

when and offset

The when element ties to the regular life events of sleeping and eating, for example:

• C = event occurs at a meal
• WAKE = event occurs [offset] after waking

An offset allows the event to be tied x minutes before or after.

The offset is an unsigned integer value so different codes within the when value-set are used to define before or after.

Event occurs at breakfast

<timing>
    <repeat>
        <when value="CM"/>
    </repeat>
</timing>

Event occurs at 1 hour before breakfast

<timing>
    <repeat>
        <when value="ACM"/>
        <offset value="60" />
    </repeat>
</timing>

Event occurs at 1 hour after breakfast

<timing>
    <repeat>
        <when value="PCM"/>
        <offset value="60" />
    </repeat>
</timing>

dayOfWeek and timeOfDay

A dosage instruction can specify days of a week and/or specific times within a day for administration.

on Monday and Thursday at 09:00 and 15:00

<timing>
    <repeat>
        <dayOfWeek value="mon" />
        <dayOfWeek value="thu" />
        <timeOfDay value="09:00:00" />
        <timeOfDay value="15:00:00" />
    </repeat>
</timing>

Note the FHIR standard states that the elements frequency and period cannot be used as well as dayOfWeek, and the elements when, frequency and period cannot be used as well as timeOfDay.

event

A dosage instruction can specify specific dates and times for administration.

on 1st Nov 2019

<timing>
    <event value="2019-11-01" />
</timing>

on 1st Nov 2019 at 10:30 and again on 1st Dec 2019 at 22:30

<timing>
    <event value="2019-11-01T10:30" />
    <event value="2019-12-01T22:30" />
</timing>

code

Allows a code, often a Latin abbreviation, for a timing schedule to be specified, for example: BID = twice a day