Diacetylmorphine is a semi-synthetic opioid. It is the 3,6-diacetyl derivative of morphine (hence diacetylmorphine) and is synthesised from it by acetylation. The white crystalline form is commonly the hydrochloride salt, diacetylmorphine hydrochloride. It has a high addiction potential, and frequent administration may cause a rapid development of tolerance by the user, especially when compared to other substances, though occasional use may not lead to symptoms of withdrawal.
Internationally, diacetylmorphine is controlled under Schedules I and IV of the Single Convention on Narcotic Drugs. It is illegal to manufacture, possess, or sell in the United States; however, under the name diamorphine, it is a legal prescription drug in the United Kingdom. Popular street names for diacetylmorphine are heroin, gear, shit, cheese, diesel, smack, B, skag, Bobby, black tar, horse, junk, jenny, brown, brown sugar, dark, Dope and H.
Diacetylmorphine deacetylates rapidly to 6-monoacetylmorphine and then to morphine. The immunomodulatory effects of diacetylmorphine are under investigation by several groups.