in the last month what was the last dose of sucralfate prescribed to patient 57023?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 57023 ) and prescriptions.drug = 'sucralfate' and datetime(prescriptions.startdate,'start of month') = datetime(current_time,'start of month','-1 month') order by prescriptions.startdate desc limit 1