instruction: what are the three top most commonly prescribed drugs until 4 years ago?
response: SELECT t1.drug FROM (SELECT prescriptions.drug, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM prescriptions WHERE DATETIME(prescriptions.startdate) <= DATETIME(CURRENT_TIME(), '-4 year') GROUP BY prescriptions.drug) AS t1 WHERE t1.c1 <= 3