I wouldn't want to try and use cocaine to focus. While I've tried it once, I don't like the typical routes of administration, the lack of quality control, and financially, supporting the drug cartels.
The only drug I use regularly is caffeine, also (coffee) =).
Hmm, I think most people who take cocaine just chew coca leaf, which eliminates all three of your concerns. There may not be any people taking cocaine by that route anywhere near you, though.
The only drug I use regularly is caffeine, also (coffee) =).