what is the name of the drug that patient 19427 is first prescribed via oral route in 11/2105?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 19427 ) and prescriptions.route = 'oral' and strftime('%y-%m',prescriptions.startdate) = '2105-11' order by prescriptions.startdate asc limit 1