Yes, there is pervasive drug use throughout the book. Some of the use is in the category of folk-magic, indigenous use of "natural" drugs in rituals. Some use is in the category of mind-destroying, addictive chemicals, creating a person easily manipulated through that addiction. Some use is in the the category of designer drugs to create a specific effect in a person's mental state.

What do we have today? All these same categories. And, as regards the third type, we have a far more plentiful and effective medical arsenal of drugs to treat particular mental issues now than we did when the book was written. The book discusses designer drugs as a way to increase particular mental abilities, not to treat particular mental maladies. But it isn't a too-far creative leap for the author to imagine drugs that can enhance rather than merely heal.