what was the amount of normocarb prescribed to patient 28484,, in total, until 63 months ago?
select sum(prescriptions.dose_val_rx) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 28484 ) and prescriptions.drug = 'normocarb' and datetime(prescriptions.startdate) <= datetime(current_time,'-63 month')