Kyle
Assuming you have an association between the parent object of your page and the selected medication, you can create a microflow that is called when you click on the new medication and sets the selected medication association with the alternate medication you selected. If the alternate medications are in a datagrid, set the microflow you created as the default action on the datagrid, and when you double click (or single click if the grid is configured for that) on a medication, the association will be reset.
Hope that helps,
Mike