what was the last drug that patient 80645 was prescribed via the iv route in 12/2104?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 80645 ) and prescriptions.route = 'iv' and strftime('%y-%m',prescriptions.startdate) = '2104-12' order by prescriptions.startdate desc limit 1