For some, no drug use includes caffeine which is a stimulant drug. Some will accept drugs such as codeine or morphine for medical reasons. Some followers of Straight Edge will not use Ny-Quil or Day-Quil because they contain alcohol. Those Straight Edgers who quit casual or illegal sex would not have one-night stands and will wait until they are in a committed relationship to have sex.
Some cities have associated straight edge as gang affiliation, but advocates call it a way of life such as being a vegetarian.