what was the drug patient 2127 had been prescribed until 20 months ago two or more times.
select t1.drug from ( select prescriptions.drug, count( prescriptions.startdate ) as c1 from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 2127 ) and datetime(prescriptions.startdate) <= datetime(current_time,'-20 month') group by prescriptions.drug ) as t1 where t1.c1 >= 2