Originally Posted by
Wheever
Yes, since Imodium is an anti-chologenic, you'll tend to retain more water when you take it, and you also won't have to pee as much--also a helpful thing when biking, helping keep the water in your system and keeping you hydrated.
As to your worries about "keeping something in..." all you're doing is delaying it so it comes out when it's more convenient. Imodium is pretty benign, which is why it's available OTC, it's not addictive, and you'll only be taking it intermittently, anyway. Give it a shot. It won't hurt you, and could well be a huge improvement in enjoying early morning rides!
Small point of information: Imodium (loperamide) is not an anticholinergic, but actually an opioid, which doesn't cross the blood-brain barrier. It is correct, however, that anything which decreases gut motility will potentially increase water absorption by the large bowel.