drug abuse among the homeless

An excellent (albeit disturbing) article detailing the lowest of SF's
homeless population.  While not a direct commentary on drug abuse, it
is grossly evident what an impediment it is in the lives of these
people.  I have never read a more persuasive argument for not using
heroin...

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/11/30/MNG263BHKR1.DTL

How do we help these people?  

Adam