The shot (I don't know the name either, but it is a big one that they put in your bum) worked well for me. I had severe diarrhea as well, and had to be hydrated many times. I cannot empahsize the need for hydration enough. If he cannot keep the fluids in him, then he MUST go to the infusion room or ER and get some fluids. Dehydration will make him tired, short of breath, dizzy, etc. I took 6-8 Lomotil as well...though it didn't always work.
Good luck to him. Don't be afraid to take him in for hydration...you won't believe what a couple of bags of fluid will do to make him feel better. I would call his oncologist ASAP and make them aware of the situation as well.
Good luck.
Cats