It is not good to eat fiber foods this soon, they are not the same as Citrucel. He can take up to 8 Imodium daily. I took Metamucil 3 times a day and Imodium 4 times a day and had a lot of BM's but not that many. Had he tried Metamucil? I'm assuming Citrucel works better. I used Metamucil clear capsules so I didn't have to swallow the gook and could easily swallow them with the minimal amount of water. I took them before I ate and drank water after I ate. You might have him ask his doctor for a prescription for Loperamide, which is Imodium in capsule form. I like it better as it acts faster so I can tell if I need more. I use to end up taking too much Imodium sometimes before and he doesn't want to do that either.
Bagels and pasta are good foods to thicken things up too. I was told to eat white breads etc. and not to eat fiber in the beginning. The Metamucil is to suck up the water that the colon is no longer there to take out of our system. Eating fiber will move things along faster and make him go more often.
Good Luck