Morphine, the principal active agent in opium, is a powerful opioid analgesic drug. Like other opiates, morphine acts directly on the central nervous system (CNS) to relieve pain, and at synapses of the arcuate nucleus, in particular. Side effects include impairment of mental performance, euphoria, drowsiness, lethargy, and blurred vision. It also decreases hunger, inhibits the cough reflex, and produces constipation. Morphine is usually highly addictive, and tolerance and physical and psychological dependence develop quickly. Patients on morphine often report insomnia and nightmares.

Morphine was first isolated in 1803 by the German pharmacist Friedrich Wilhelm Adam Serturner, who named it 'morphium' after Morpheus, the Greek god of dreams. But it was not until the development of the hypodermic needle (1853) that its use spread. It was used for pain relief and, ironically, as a 'cure' for opium or alcohol addiction. Its extensive use during the American Civil War resulted in over 400,000 sufferers from the "soldiers disease" (addiction).

Formal Chemical Name (IUPAC)
7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diol