when was patient 10266 prescribed a medication via pr route the first time during their first hospital visit?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 10266 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) and prescriptions.route = 'pr' order by prescriptions.startdate asc limit 1