instruction: give me the top five most often prescribed drugs for patients 50s in 2101?
response: SELECT t1.drug FROM (SELECT prescriptions.drug, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.age BETWEEN 50 AND 59) AND STRFTIME('%y', prescriptions.startdate) = '2101' GROUP BY prescriptions.drug) AS t1 WHERE t1.c1 <= 5