Remember, opiate constipation is caused because opiates cause a slowing in the motility of the gut. That is the movements the bowels normally have, peristalsis, don't happen quite the same way or as quickly as normal.

A good stool softner can really help. Look for Docusate Sodium I think it is. As a prescription it was called Colace. It does nothing but soften the stool. Laxatives taken long term can cause problems on their own.

Lottsa fluids and a bit of fiber can help. But as has been pointed out be careful with the fiber.

Magnesium can help as well. I take SloMag for my PN anyway but when constipation gets to be an issue I take one on an empty or almost empty stomach. It really does seem to help.