what was the drug name of the drug that was first prescribed to patient 53089 during the first hospital encounter?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 53089 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) order by prescriptions.startdate asc limit 1