Read the imodium packaging instructions. (BTW, go to your OP and hit EDIT, to correct your thread title, that reads imodiCum) I think you get best results with imodium after about 6 hours. And now I'm gonna get a bit graphic, so don't read further if you're prudish. But neither slam me if you do read on, since you've been warned.
If you're gonna have to wait that long, just don't eat if you expect to be having sex. I'm kinda regular. I take the toilet after waking in the morning and usually not for the rest of the day except to pee.
So I try to time my bottoming to between about noon and 7 or 8, not having any big meals. When I was single I required the top to wear a condom, so his dick was gonna stay clean in any case. If he couldn't tolerate a little dirt on his rubber then frankly he was in the wrong business.
With my HIV negative husband who barebacks me, I douche with a rubber bulb thingy, that flushes the rectum as far as he reaches. I don't do a complete colonic cleanse or enema. That method works fine. For US, it may not work for you.
If you're not regular in your bowel movements (and I've been all my life) you may want to look at your diet, possibly talk with your doctor. You may uncover another underlying issue that needs attention. I note your height & weight in your profile, which sounds like a skeleton. If accurate, you might want to see your doctor anyway, on that issue alone.