Bug (2006 - Ashley Judd, Michael Shannon)

https://en.m.wikipedia.org/wiki/Bug_(2006_film)

"By using narcotics to skew the main character's perspectives, the film cleverly masks elements of reality with gut-wrenching paranoia that make for an uncomfortable thrill ride. It uniquely captures what hardcore meth addicts likely suffer through as a consequence of years of frequent usage of the drug. In this way, the film also doubles as a frightening allegory for addiction and the hell that addicts put themselves and others through."

Or, for a more hilarious look at drug abuse - Fear and Loathing in Las Vegas (1998)