Heroin (diacetylmorphine or morphine diacetate, also known as diamorphine (BAN, INN) and commonly known by its street names of H, smack, horse, brown, black, tar, and others) is an opioid analgesic originally synthesized by C.R. Alder Wright in 1874. 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.