re: Overdosing on Immodium AD is a thing now

It produces opiate-like toxicity because it targets mu opioid receptors. Structurally, it is a combination of meperidine and methadone. It is generally considered to not have CNS activity because it poor dissolution, roughly 40% bioavailability, and is a strong substrate for efflux (gets pumped out as quickly as it gets in). There have been studies performed that show nanoparticles packed with loperamide and coated with polysorbate 80 can sneak into the CNS and cause the typical opioid effects.