A once-a-day pill has been proven to lower the risk of getting HIV among needle-using drug addicts, just as it does among heterosexual couples and men who have sex with men.
http://www.wnyc.org/npr_articles/2013/jun/13/prevention-pill-cuts-hiv-risk-for-injecting-drug-users/
http://www.wnyc.org/npr_articles/2013/jun/13/prevention-pill-cuts-hiv-risk-for-injecting-drug-users/