count the number of times that patient 73713 was prescribed 5% dextrose in this month.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 73713 ) and prescriptions.drug = '5% dextrose' and datetime(prescriptions.startdate,'start of month') = datetime(current_time,'start of month','-0 month')