Morphine
Morphine (INN) (IPA: ) is a strong opiate pain killer drug. It is the principal active agent in opium and the prototypical opiate.  Like other opioids, e.g. diacetylmorphine (heroin), morphine acts directly on the central nervous system (CNS) to relieve pain, and at synapses of the nucleus accumbens in particular.  Morphine is highly addictive when compared to other substances, and tolerance and physical and mental dependences develop very rapidly.