Codeine - An alkaloid of opium extracted from morphine. Codeine's effects resemble those of morphine but with only one-sixth to one-tenth of the analgesic action. Codeine is commonly found in cough medicine and minor prescription pain relievers.

Heroin - highly addictive drug derived from morphine, is obtained from the opium poppy. It is a "downer" that affects the brain's pleasure systems and interferes with its ability to perceive pain. Heroin can be injected into a vein or a muscle; smoked through a water pipe or standard pipe; mixed in a marijuana joint or regular cigarette; inhaled as smoke through a straw or as powder through the nose. Heroin users quickly develop a tolerance for the drug and need more and more to get the same high.

Opiates - a major class of drugs that depress the central nervous system and are used principally to relieve pain. Examples include morphine, heroin, and codeine.