count the number of times spironolactone had been prescribed to patient 54894 since 5 years ago.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 54894 ) and prescriptions.drug = 'spironolactone' and datetime(prescriptions.startdate) >= datetime(current_time,'-5 year')