Existing Wording
MedicationPrescription.dosageInstruction.scheduled[x] as Type dateTime|Period|Timing

Cannot see how to express common frequency ranges: Every 4-6 hours, etc.

Comments
see CDA Examples Task Force: Patient prescribed medication every 4 to 6 hours (https://github.com/jddamore/HL7-Task-Force-Examples/blob/master/MED_Med_Every_4-6_hrs.xml) for example in CDA.

Grahame's Comments
Guess this would be in Timing. Need to look at all the tasks relating to Timing.