instruction: what were the four most frequent drugs that were prescribed in the same month to the valve replacement >= 7 days female patient with age 60 or above after having been diagnosed with valve replacement >= 7 days, until 2104?
response: SELECT t3.drugname FROM (SELECT t2.drugname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM (SELECT patient.uniquepid, diagnosis.diagnosistime FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'valve replacement >= 7 days' AND STRFTIME('%y', diagnosis.diagnosistime) <= '2104') AS t1 JOIN (SELECT patient.uniquepid, medication.drugname, medication.drugstarttime FROM medication JOIN patient ON medication.patientunitstayid = patient.patientunitstayid WHERE patient.gender = 'female' AND patient.age >= 60 AND STRFTIME('%y', medication.drugstarttime) <= '2104') AS t2 ON t1.uniquepid = t2.uniquepid WHERE t1.diagnosistime < t2.drugstarttime AND DATETIME(t1.diagnosistime, 'start of month') = DATETIME(t2.drugstarttime, 'start of month') GROUP BY t2.drugname) AS t3 WHERE t3.c1 <= 4