when was the first time until 10/2101 that patient 41816 was prescribed a medication via iv route?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 41816 ) and prescriptions.route = 'iv' and strftime('%y-%m',prescriptions.startdate) <= '2101-10' order by prescriptions.startdate asc limit 1