I'm an introvert, and my drug of choice has changed over time for sure. however, what I've sought out in drugs tends to be the same. when I was addicted to speed for about a year, I used alone almost exclusively - I would spend my time writing compulsively for hours or reading or doing homework. being very productive, and feeling that social interaction was a frivolous waste of time.
before that, as well as now, the drug of choice was certainly "downers". for the past 6 months or so I've been into / addicted to opiates (morphine, codeine, oxycodone, hydrocodone) and also using Soma and benzos. I like to escape - pardon the cliche - from my reality: be it emotional/mental or physical. I find the world opiates and downers open me up to is solely mine - a private emptiness enjoyed in private -in my room, behind closed doors and closed eyes...and a closed/closing mind. or rather, a mind that is simply elsewhere.