Antidepressants enhance the sensation of orgasm. Sometimes so much that it darkens in the eyes. However, it is difficult to achieve ejaculation when taking antidepressants.
As far as I know, narcotic substances (not to be confused with psychotropic ones) depress the nervous system.
I do not think that drugs help or hinder the achievement and duration of orgasm. Another thing is that the practice of "controlling orgasm" is widespread.