This pop-up occurs when you prescribe a medication that is not part of the database. The medication will appear in italics, and since the program does not recognize the medication, it asks you to affirm that it is NOT a controlled substance.
I do not believe you can turn off this pop-up. What you can do is find the medication in the database (usually) and prescribe it as a recognized (non-italicized) drug. It will then skip the attestation message.
