Opiate refers to natural drugs whereas opioid refers to synthetic substances derived from or resembling the substances in the poppy plant. Opioids act like opiates on the same receptors in the brain and are mainly used to relieve pain. Some of the commoner opiate drugs are: Codeine, heroin (diacetylmorphine), pethidine, methadone, morphine and diconal. Morphine and codeine are extracted from opium and heroin is manufactured chemically from morphine. When injected, swallowed or smoked, opiates enter the bloodstream and quickly affect the brain. In the brain the drug is converted into monoacetylmorphine and morphine. It is the morphine molecule that binds with opioid receptors in the brain. The routes of administration for opiates are: oral, subcutaneous, intramuscular, intravenous, rectal, transdermal and transmucosal. The medical applications of opiates include effective relief of pain, treatment for diarrhoea and vomiting and as a cough suppressant. The most popular of opiates as an illicit drug of misuse is heroin. Methadone is a synthetic opioid, used therapeutically as an analgesic and in the treatment of opiate addiction. Methadone maintenance treatment is the most employed agent used in substitution treatment for heroin addiction around the world and is still regarded as the most effective.