Try this one:
The user selects the Filter type (By Patient or By Drug)
If "by Drug" is selected, the user can then select a drugname.
The records are filtered by drug name, and the user then has the option of selecting a "from" date.
If the "from" date is selected the records are filtered to show only those with the drug name and a date greater than or equal to the "From date".
The user can then select a "To" date, which filters the records further.