When people complain about constipation in newts/sals, it's usually that the animal has ingested a rock, or the animal happens to be fat and hasn't pooped recently, or the animal is bloated. None of these are really constipation. And if it is constipation, I don't know of anything you could do other than keeping the animal on moist substrate (as usual) and wait for things to pass.
What has been his diet? Is Abe housed by himself, or with others?