Final answer:
Hallucinogens are classified on their own due to their complex and profound effects on sensory and perceptual experiences, making them distinct in the realm of psychoactive drugs.
Step-by-step explanation:
The drug given its own classification category due to its complex effects at different doses is hallucinogens. Hallucinogens are a class of drugs that result in profound alterations in sensory and perceptual experiences, often causing vivid hallucinations.
While many drugs have multiple effects and can be placed in various categories, hallucinogens show a wide variance in terms of neurochemical interaction and the resulting subjective experience, which makes them distinct enough to have their own category.