how much d5 1/2ns was prescribed to patient 23002 last in 10/this year?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 23002 ) and prescriptions.drug = 'd5 1/2ns' and datetime(prescriptions.startdate,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m',prescriptions.startdate) = '10' order by prescriptions.startdate desc limit 1