MSIR

Morphine (INN) (pronounced /ˈmɔrfiːn/) (MS Contin, MSIR, Avinza, Kadian, Oramorph, Roxanol) is an extremely potent opiate analgesic psychoactive drug, is the principal active ingredient in Papaver somniferum (opium poppy, or simply opium), is considered to be the prototypical opioid. In clinical medicine, morphine is regarded as the gold standard, or benchmark, of analgesics used to relieve severe or agonizing pain and suffering. Like other opioids, e.g. oxycodone (OxyContin, Percocet, Percodan), hydromorphone (Dilaudid, Palladone), and diacetylmorphine (Heroin), morphine acts directly on the central nervous system (CNS) to relieve pain. Morphine has a high potential for addiction; tolerance and both physical and psychological dependence develop rapidly.

Source: http://en.wikipedia.org/wiki/Morphine