Heroin is a depressant drug that slows down the body and the brain. It is the purist form of a group of drugs called opioids. Other opioids include codeine, methadone, morphine and pethidine. Opioids are manufactured from the opium poppy plant. The quality of heroin can vary greatly because dealers mix the powder with other substances to make their supply go further. Heroine can be injected, smoked or snorted.