Imodium and Lomotil are totally different classes of drugs never mind prescription or over the counter. Imodium is a pure anti-diarrheal. Lomotil has both anti-spasmodic and anti-diarrheal properties. There should be no confusion about this and everyone should understand what these drugs do when you put them in your body. I was given Lomotil due to a very spasmodic Pouch after takedown which is not the same thing as a runny pouch. A spasmodic Pouch is one that causes bursts of bowel movements right after meals, due to excessive peristalsis. If you throw Imodium at that issue it will not go away and will get worse.
Slouchy, you are probably right that sophisticated and veteran narcotic users know how to counteract Imodium with high powered laxatives. I had a client who had triple cervical fusion surgery and told him to take it easy with the pain meds they gave him and he stated to me he could not get constipated because he has ulcerative colitis. Well he ended up having to have an emergency fecal disimpaction. I will spare you all the details of that procedure but my client likened it to a horrible medieval torture. He is now very afraid to take any pain meds.