when was the last time until 6 months ago that patient 9297 was prescribed a medication via vg?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 9297 ) and prescriptions.route = 'vg' and datetime(prescriptions.startdate) <= datetime(current_time,'-6 month') order by prescriptions.startdate desc limit 1