Heroin (diacetylmorphine (INN)), also known as diamorphine (BAN), or, especially in older literature, as morphine diacetate, is an opioid analgesic synthesized from morphine, a derivative of the opium poppy. When used in medicine it is typically used to treat severe pain, such as that resulting from a heart attack. It is the 3,6-diacetyl ester of morphine, and functions as a morphine prodrug (meaning that it is metabolically converted to morphine inside the body). The white crystalline form considered "pure heroin" is usually the hydrochloride salt, diacetylmorphine hydrochloride. When heroin is supplied illegally, though, it is often adulterated to a freebase form, dulling the sheen and consistency to a matte white powder. As of 2004, roughly 87% of the world supply of opium and its derivatives, including heroin, was thought to be produced in Afghanistan. However, production in Mexico has risen six-fold from 2007 to 2011, changing that percentage and placing Mexico as the second largest opium producer in the world.
As with other opioids, diacetylmorphine is used as both an analgesic and a recreational drug. Frequent and regular administration is associated with tolerance and physical dependence, which may develop into addiction. Internationally, diacetylmorphine is controlled under Schedules I and IV of the Single Convention on Narcotic Drugs. It is illegal to manufacture, possess, or sell diacetylmorphine without a license in almost every country.
Under the chemical names diamorphine and diacetylmorphine, heroin is a legally prescribed controlled drug in the United Kingdom, and is supplied in tablet or injectable form for the same indications as morphine is, often being preferred over morphine due to its lower side effect profile. It is also available for prescription to long-term users in the Netherlands, United Kingdom, Switzerland, Germany and Denmark alongside psycho-social care, and a similar programme is being campaigned for by liberal political parties in Norway.