Issued_Prescription is intended to be set "post-emission", by the Practitioner.
It is an audit trail of prescriptions that are associated with a given symptom, and useful for historical analysis.
As such, it is very different from every other field in the Symptom, all of which are immutable and provide real-time guidance to the practitioner. In fact, if we are to consider auditing/historical-analysis, perhaps we should do it holistically across all primary types.