what is the amount of isosorbide dinitrate sa that was prescribed to patient 55360 for the last time on the current hospital visit?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 55360 and admissions.dischtime is null ) and prescriptions.drug = 'isosorbide dinitrate sa' order by prescriptions.startdate desc limit 1