unable to change constraints?

Hello,

I created a table with primary key constraint then I added 2 foreign key constraints, but we changed our naming convention and I wanted to update one of the constraint names but when I promote the script it tells me it failed because constraint 1 was already created.

When I add or change constraints do I need to update the source with Drop commands? or comment out previous commands? what is supposed to be the technique for managing the source for constraints on a table?