list the top four most frequent drugs that patients have been prescribed with within the same hospital visit after they had been prescribed with pyridoxine during the previous year.
select t3.drug from ( select t2.drug, dense_rank() over ( order by count(*) desc ) as c1 from ( select admissions.subject_id, prescriptions.startdate, admissions.hadm_id from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'pyridoxine' and datetime(prescriptions.startdate,'start of year') = datetime(current_time,'start of year','-1 year') ) as t1 join ( select admissions.subject_id, prescriptions.drug, prescriptions.startdate, admissions.hadm_id from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where datetime(prescriptions.startdate,'start of year') = datetime(current_time,'start of year','-1 year') ) as t2 on t1.subject_id = t2.subject_id where t1.startdate < t2.startdate and t1.hadm_id = t2.hadm_id group by t2.drug ) as t3 where t3.c1 <= 4