instruction: what was the drug that was prescribed to patient 66411 via the os route on the first hospital visit for the first time?
response: SELECT prescriptions.drug FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 66411 AND NOT admissions.dischtime IS NULL ORDER BY admissions.admittime LIMIT 1) AND prescriptions.route = 'os' ORDER BY prescriptions.startdate LIMIT 1