for the first time during their first hospital encounter, how much sodium bica was prescribed to patient 25723?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 25723 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) and prescriptions.drug = 'sodium bica' order by prescriptions.startdate asc limit 1