The Pre-Existing Meds displays the pre-existing medications for the patient. Medications that were added manually, and therefore cannot be checked for interactions, will have the [NDI] appended to them to indicate that there is No Drug Interaction information available.
Clicking the * button next to a medication allows you to view the prescribed information along with the ability to view any drug interactions for a medication, as well as renew, or discontinue the medication via the face sheet.