When I was in the hospital years ago, they gave me the 5-ASAs every 8 hours - like, 6 am, 2 pm, bedtime. I tried to follow that for years at home, and try to follow that for my kid (though, with a teen in summer, it's on a much, much later schedule....)
Now I take them 4 times a day, so I do breakfast, lunch, dinner, bedtime.
In either case, I've always done some at bedtime and then done the enema. I figure it's a good amount of time before the oral pills meet with with the Rowasa from the other end...
I've never had gastro distress from taking asacol on an empty stomach but have sometimes had a small snack with them "just in case."
I hope this is just the ticket for you - both ends, hooray!