what was the simethicone dosage that patient 5395 was first prescribed since 49 months ago?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 5395 ) and prescriptions.drug = 'simethicone' and datetime(prescriptions.startdate) >= datetime(current_time,'-49 month') order by prescriptions.startdate asc limit 1