Complex sentence: At doses higher than medically recommended, dextromethorphan is classified as a dissociative hallucinogenic drug and (DRI) Dopamine Receptor Inhibiting Noting visible effects that are similar to those of ketamine and phencyclidine (PCP).
Split into simpler sentences: At doses higher than medically recommended, dextromethorphan is classified as a dissociative hallucinogen. Certain effects that are similar to the dissociative agents ketamine and phencyclidine (PCP).