how much ns was prescribed during this month for the first time to patient 76332?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 76332 ) and prescriptions.drug = 'ns' and datetime(prescriptions.startdate,'start of month') = datetime(current_time,'start of month','-0 month') order by prescriptions.startdate asc limit 1