(b) : Morphine is an potent opioid analgesic used mainly to relieve severe and persistent pain, particularly in terminallyill patients or who haveundergone surgery. It also induces feelings of euphoria. It is administered by mouth, injection, or in suppositories. Common side­ effects are nausea and vomiting, constipation, and drowsiness. With regular use, tolerance develops and dependence may occur.