Morphine (sold under nearly a hundred trade names) is an opioid analgesic drug, and the main psychoactive chemical in opium. In clinical medicine, morphine is regarded as the gold standard of analgesics used to relieve intense pain. Like other opioids, such as oxycodone, hydromorphone, and diacetylmorphine (heroin), morphine acts directly on the central nervous system (CNS) to relieve pain. Morphine has a high potential for addiction; tolerance and psychological dependence develop rapidly, although physiological dependence may take several months to develop.