instruction: what was the last time patient 7742 was prescribed vancomycin hcl and ondansetron odt in 03/2103, at the same time?
response: SELECT t1.startdate FROM (SELECT admissions.subject_id, prescriptions.startdate FROM prescriptions JOIN admissions ON prescriptions.hadm_id = admissions.hadm_id WHERE prescriptions.drug = 'vancomycin hcl' AND admissions.subject_id = 7742 AND STRFTIME('%y-%m', prescriptions.startdate) = '2103-03') AS t1 JOIN (SELECT admissions.subject_id, prescriptions.startdate FROM prescriptions JOIN admissions ON prescriptions.hadm_id = admissions.hadm_id WHERE prescriptions.drug = 'ondansetron odt' AND admissions.subject_id = 7742 AND STRFTIME('%y-%m', prescriptions.startdate) = '2103-03') AS t2 ON t1.subject_id = t2.subject_id WHERE DATETIME(t1.startdate) = DATETIME(t2.startdate) ORDER BY t1.startdate DESC LIMIT 1