what was the name of the drug that patient 25733 was prescribed for the last time in this hospital encounter via po route?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 25733 and admissions.dischtime is null ) and prescriptions.route = 'po' order by prescriptions.startdate desc limit 1