We are constantly pulling energy into ourselves. This function is unconscious and often undiscerning. When you are among a group of people, you will draw upon the ambient energy that is generated by that group. Occasionally, there is a quality to the energy of a group that you may not wish to take into yourself. This is especially true if many of the individuals in the group are tainted in some way, as with illness, intoxication, or drug-use.
Rather than shielding yourself and thus blocking yourself off from all the energy in the room, you may set up a filter. Less rigid and opaque than a true shield, a filter allows you to sort through all that you take in and block certain elements of that energy out. A filter may target certain emotions which you do not wish to vicariously experience or they may filter out the taint of alcohol, drugs, or disease so you do not draw these things into yourself during a general crowd feed.
Target the specific energy that you do not wish to take in. Visualize a filter, like a porous shield, that will allow everything to pass through except this particular energy. If you are actively drawing from the crowd around you, simply be selective in what you pull into yourself through nets or tendrils. Isolate the unwanted energy from everything else and discard it before you actively pull the rest through. All this requires is an awareness of yourself and your surroundings on the subtle level.
A filter can also be used to take only a specific sort of energy in. Simply isolate that element among the ambient energy, focus on it, then draw upon it to the exclusion of all else. As the subtle and the physical are intricately interwoven, this can work on chemicals present in your target's system. Though physical contact facilitates this technique, it can be done with effort from a distance. In this way, you can focus on the drugs in someone's system and pull them away, thus robbing them of their high. Treat the drugs as you would any intrusion on the subtle level, grabbing onto them with your subtle body but not pulling them into yourself.
If you grab onto the drugs or alcohol present in another's system in this way and pull them into yourself, you will experience the effects of the drugs vicariously. Sometimes this is desirable. Simply focus on someone who is suitably intoxicated, focus on the element present in their systems that is responsible for the intoxication, and draw it into yourself. Once again, this is most efficiently done with person to person physical contact, but can be effected in a group or long-distance draw.
Because you have the ability to manipulate energy on such a level, you can also consciously burn the resulting intoxication out of your system whenever you choose. Simply extend your awareness within yourself, focus on the intoxicant, gather it up and cast it away. This works to a certain degree even it you have physically imbibed the intoxicant.