what was the last drug until 52 months ago that patient 2700 was prescribed via the ou route?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 2700 ) and prescriptions.route = 'ou' and datetime(prescriptions.startdate) <= datetime(current_time,'-52 month') order by prescriptions.startdate desc limit 1