Morphine. Molecular graphic of morphine, a pain- killing (analgesic) drug (formula: C17H19NO3). Morphine is a drug derived from opium, present in the seeds of some species of poppy. The atoms are spherical and colour-coded: carbon (blue), oxygen (red), hydrogen (white) and nitrogen (light blue). Morphine is a powerful painkiller, and produces a sense of euphoria and dreaminess. It acts at receptors in the body which are naturally triggered by endorphins, the body's natural painkillers. It is addictive with prolonged use, and higher and higher doses are needed to produce the desired effect (tolerance). Side-effects include constipation, vomiting and nausea.