The Harm Reduction Model of response to drug abuse?

I have to explain the The Harm Reduction Model of response to drug abuse, and in my college book, i cant find a solid definition. Any help would be greatly appreciated .

More Meth Drug Addiction Info:

• » Tobacco Harm Reduction 2010 Now Out – Ashtray Blog: An …
• Russian youth struggle with drink and drug abuse – 27 Feb 08
• Drug abuse and vitamin deficiency | Mikes.spb.su table
• Santa Cruz area residents 'blissfully unaware' of illegal drug …
• Risks And Measures For Preventing Drug Abuse Among Children And …
• Causes, Treatment & Prevention Of Drug Abuse Training Video
• Issues: Abbotsford's Anti-Harm Reduction Bylaw (Sort Of …
• Houston Texas Drug Abuse Prevention | Treatment Alcohol
• Opiate overdoses spike to alarming levels « For those who can't …
• US ends 'war on drugs' | The NORML Stash Blog