A little while ago there were reports that Africans were smoking antiretroviral drugs, as though that offered “highs” and could be addictive.
Clark Baker has written a fascinating discussion with evidence that Sustiva a.k.a. Efavirenz might indeed be addictive:
http://exlibhollywood.blogspot.com/2009/05/has-sustiva-solved-hiv-mystery.html