with opioids, one of the things that happens is that your gut, your gastrointestinal system, slows down the receptors. Your body is trying to compensate by speeding up the gastrointestinal tract. So when the drug abruptly leaves after several weeks of constant administration of the opioid, now the body is unprepared for the drug not being there and it overcompensates. It really ramps up the motility of the gastrointestinal tract

That's the best description of explosive diarrhea I've ever read lol