Heroin, so benign in the hands of doctors, becomes highly dangerous when it is cut by black-market dealers - with paracetamol, drain cleaner, sand, sugar, starch, powdered milk, talcum powder, coffee, brick dust, cement dust, gravy powder, face powder or curry powder. None of these adulterants was ever intended to be injected into human veins. Some of them, such as drain cleaner, are simply toxic and poison their users. Others - sand or brick dust - are carried into tiny capillaries and digital blood vessels where they form clots, cutting off the supply of blood to fingers or toes. Very rapidly, venous gangrene sets in, the tissue starts to die, the fingers or toes go black and then have only one destiny: amputation. Needless suffering - inflicted not by heroin, but by its black-market adulterants.