(1) A prescription written by a practitioner licensed in a state or territory of the United States, other than Oregon, may be filled only if the pharmacist called upon to fill such prescription determines, in the exercise of professional judgment:
(a) That it was issued pursuant to a valid patient-practitioner relationship; and
(b) That it is authentic.
(2) However, if the practitioner writing the prescription is not known to the pharmacist, the pharmacist shall obtain proof to a reasonable certainty of the validity of the prescription.
(3) The provisions of ORS 689.515 authorizing generic substitution shall not apply to prescriptions described in this section unless authorized on the prescription.