Generally, when you prescribe a medication for the first time it becomes part of your "Favorites"/"Short-List" so that it gets prioritized in future searches. However, occasionally you want to remove a medication from this list because it's one you not longer want to use (it's been discontinued from manufacture, you prefer a different brand, etc).
To remove a medication form your "favorites", you can actually remove the item while you're searching for a medication to prescribe in a patient's chart:
1. Click the (+) button on the patient's Medication block to add a new medication
2. Search for the medication you want to remove
3. When you see it, right-click the offending medication ( Ctrl+click on a Mac) and select the option to "Add/Remove as preferred Rx":
As soon as that's been done the drug will no longer show up in your preferred search list, but it will still show up on the extended search (which you can trigger by adding a "+" to your search term or by adding search terms until no matches can be found on your favorites list.