From Seed to Seed:
Plant Science for K-8 Educators

Opium. The medicinal use of opium can be traced back to at least 4000 B.C., and its derivatives are still used today. The source of opium is the opium poppy, Papaver somniferum. The immature seed capsules of this plant contain a resin that is dried to make raw opium.

The chemical responsible for the sedating effects of opium is the alkaloid morphine. Morphine depresses the digestive and respiratory systems, and relieves pain. It is used medicinally as a sedative; however, individuals who abuse morphine-based substances soon develop increased tolerance to the drug so that more and more is needed to produce the desired effects. This often results in both psychological and physical addiction. Codeine, another derivative of morphine, is also used in medicines to suppress coughing and relieve pain.

Opium also provides the raw material for making heroin, a very potent and addictive narcotic. Although codeine and morphine are less intensely addictive than opium and heroin, they are still highly regulated substances.

Opium is a good example of a substance that is poisonous in large doses, but whose medical derivatives have curative powers in small, carefully regulated doses.