tab,

It does reduce pain and allow a Domme to go harder than what you might normally take. So, for example, you may have an amazing fantasy about being caned and want the marks afterwards but may have failed to take that level of pain under normal circumstances. If you have been forced to drink alcohol and are buzzed (not falling down drunk) or been made to take pain killers (such as vicodin) then it will allow the Domme to go harder and go past the point where you normally would use a safeword because of the pain but still be totally in the session.

The mindfuck part of it (which is really what good Forced Intox is about IMO), could be Domme telling you that she is forcing you to drink/take pills specifically so that she can turn your ass into a bloody pulp and that you won't be able to sit on for the next week without pain. For humiliation, she could add in comments about how she doesn't have to do this with her better clients but that you are such a wimp that this is the only way she can really have her sadistic fun with you. But, that is all dependent on what gets you excited.

The downside of using it for a sadistic session is that what most people get out of pain is that endorphin rush (which is essentially a drug) that can push into subspace. The endorphin rush isn't triggered by the fact you are getting hit, it is pain response so if you don't have that level of pain you aren't going to get that same release. I can see it for a sadistic session in the way I have mentioned, but I do think it would lose something because of the lesser (or lack of) endorphin release.

To me forced intox is actually best for mindfucks (since you're not all there mentally to discern things as well) and pushing limits since it lowers your inhibitions and allows you to agree to things that when you are perfectly sober you may never agree to (this should also serve as a warning to anyone before they agree to it).