If they work to the extent of stopping someone damaging their limb, then those would be preferable. (Assuming the side effects are better than having a prosthetic.)

Edit: I quick look on the internet suggests that there are treatments to help reduce the distress and depression associated with the condition, but there isn't anything that fully removes the desired to get rid of the limb.

So you still need to determine if the patient is going to try to amputate themselves unsafely. If so they're better off if an expert does it in safe conditions.