what was the name of the drug that since 20 months ago patient 88659 had been prescribed two 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 = 88659 ) and datetime(prescriptions.startdate) >= datetime(current_time,'-20 month') group by prescriptions.drug ) as t1 where t1.c1 = 2