From my little bit of knowledge of psychology at amateur level, I expect that even sadists can apply Epicurus' philosophy because it provides both feelings and reason as input for making decisions on what action to take.
Sadists who are not psychopaths may trust their feelings as guide because they have compassion, which stops them from excessively harming their masochistic partners. They need reason mainly to carry out sadistic techniques safely to prevent unintentional hazards.
Sadists who are psychopaths need to rely much more on reason to prevent themselves from severely harming or killing people. A life-time prison sentence might not scare them at the level of feelings but reasoning about such consequences might stop them from excessive actions.