and what was the first time patient 71192 was prescribed medication using the lock route in 07/2103?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 71192 ) and prescriptions.route = 'lock' and strftime('%y-%m',prescriptions.startdate) = '2103-07' order by prescriptions.startdate asc limit 1