The mere fact that levamisole is now being found in heroin is significant, but perhaps more interestingly, it's appears it's being added to the morphine base prior to acetylation.
http://www.justice.gov/dea/programs/forensicsci/microgram/journal2011/mj8-1_16-23.pdf
http://www.justice.gov/dea/programs/forensicsci/microgram/journal2011/mj8-1_16-23.pdf
