This film is mostly meant to show the effects of various types of drugs.
The whole movie shows excessive drug use, Mainly Hallucinogens
Johnny Depp is seen smoking a cigarette with holder almost the entire film.
Illegal drugs are a main theme of the film. The two main characters are almost always abusing a drug during the film. They try many illegal drugs and the film shows each drug having a different effect on them.
The characters appear to be disoriented throughout the film and suffer the effects of each drug including prologned sequences of fear, anger and hallucinations.
A briefcase is seen near the beginning of the film, filled entirely with, quote, "two bags of grass, seventy-five pellets of mescaline, five sheets of high-powered blotter acid, a saltshaker half-full of cocaine, and a whole galaxy of multi-colored uppers, downers, screamers, laughers... Also, a quart of tequila, a quart of rum, a case of beer, a pint of raw ether, and two dozen amyls."
Gonzo vomits three times throughout the course of the film.
Hunter and Gonzo are shown drunk at three different times. They appear very disgruntled.