The word faded is used to describe someone who is not sober. It does not matter what substance or method was used to alter the person's state of consciousness; if they are under the influence of anything, they are faded.
To be under the influence of any CNS depressent to the point where your nodding off(falling asleep while doing something like reading or watching TV). Usually used in slang for marajuana or opiates, sometimes alcohol or benzodiazepines.
Jason-Damn man, I popped pills and smokepot until I got strait faded and nodded off while talking to andy in the middle of a sentence.
Tim-Ya, that oxy had me passing out in my lap for like 4 hours!