count the number of times patient 7241 was prescribed with meropenem until 3 years ago.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 7241 ) and prescriptions.drug = 'meropenem' and datetime(prescriptions.startdate) <= datetime(current_time,'-3 year')