instruction: since 91 months ago, what was the first drug patient 018-86978 was prescribed via the idrm route?
response: SELECT medication.drugname FROM medication WHERE medication.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '018-86978')) AND medication.routeadmin = 'idrm' AND DATETIME(medication.drugstarttime) >= DATETIME(CURRENT_TIME(), '-91 month') ORDER BY medication.drugstarttime LIMIT 1