Music Composers Unite!
Now I haven't read through all the replies so maybe someone has said this before but I think drugs may aid in an awakening process for the person in a whole, and give a lot of inspiration. However I think that one should strive to have that inspiration without drugs.
Also, David Lucas Burge says that people's perfect pitch abilities tend to diminish after using drugs so it's probably not a good idea to take drugs extensively.
I will usually drink a fair amount of tea whilst composing. Especially green tea and peppermint tea. I find they help me stay focused. I've never tried composing under the influence of other substances.