instruction: what was the last prescription drug that was prescribed to patient 99747 during the previous month?
response: SELECT prescriptions.drug FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 99747) AND DATETIME(prescriptions.startdate, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-1 month') ORDER BY prescriptions.startdate DESC LIMIT 1