A crystalline alkaloid (7,8-didehydro-4,5-epoxy-17-methyl-morphinan-3,6-diol), extracted from opium, the salts of which are soluble in water and are used as analgesics, anaesthetics and sedatives; it is one of a group of morphine alkaloids.
"The doctor administered a dose of morphine to manage the patient's severe pain after the surgery."