tell me the drug that was prescribed to patient 9983 for the last time until 42 months ago?
select prescriptions.drug from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 9983 ) and datetime(prescriptions.startdate) <= datetime(current_time,'-42 month') order by prescriptions.startdate desc limit 1