what was the four most frequent drugs that were prescribed to patients with age 20s in the same hospital encounter after they had been diagnosed with hyposmolality until 2103?
select t3.drug from ( select t2.drug, dense_rank() over ( order by count(*) desc ) as c1 from ( select admissions.subject_id, diagnoses_icd.charttime, admissions.hadm_id from diagnoses_icd join admissions on diagnoses_icd.hadm_id = admissions.hadm_id where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'hyposmolality' ) and strftime('%y',diagnoses_icd.charttime) <= '2103' ) 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 admissions.age between 20 and 29 and strftime('%y',prescriptions.startdate) <= '2103' ) as t2 on t1.subject_id = t2.subject_id where t1.charttime < t2.startdate and t1.hadm_id = t2.hadm_id group by t2.drug ) as t3 where t3.c1 <= 4