It doesn't, actually. Loperamide IS an opiate, but it also doesn't cross the blood brain barrier. People don't actually get high from it. But what does happen, is desperate opiate abusers who are in withdrawal read about this and try downing an entire bottle to feel better.

Trust me here, when I used to be an addict, a common topic of conversation against the more chemistry inclined of opiate addicts was how to alter or refine loperamide to cross the blood brain barrier in significant enough amounts that we'd be able to be high for days while only spending a few bucks. There were rumors back in the day that some people had figured it out, but I've never known a single person who successfully got high from it, despite knowing many who tried.

Now, that being said, you can get addicted to loperamide in the sense that it does effect your stomach despite not offering an opiate high. It causes chronic constipation in the same way opiates/opioids do because the mechanism for that doesn't require the blood brain barrier to be crossed, like the dopamine you get from say, oxycodone, does. So what happens is if you take loperamide for a while and then stop, you get severe diarrhea, vomiting and stomach cramps. Which is a small portion of what opiate withdrawal entails.