for the first time, during their first hospital encounter how much cimetidine was prescribed to patient 8016?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 8016 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) and prescriptions.drug = 'cimetidine' order by prescriptions.startdate asc limit 1