I think you misunderstand Marx' statement. When he talks about opiates he is not thinking in terms of drug abuse with the intent to get high but rather as a drug intended to tranquilize or make life more palatable, which was how opiates were used by the middle classes during the 19th century. Hence he is comparing the use of opiates by the middle classes to the use of religion by the masses (or working class).
As a non-believer (although not an atheist) and as someone who doesn't drink or do drugs, I'd say that life itself has the ability to intoxicate. Expecially if you realize that there is no eternal hereafter and therefore have reason to prize every moment. As Baudelaire noted there are many ways to be intoxicated, "With wine, with poetry or with virtue, as you please."