: a synthetic version of a controlled substance (as heroin) that is produced with a slightly altered molecular structure to avoid classification as an illicit drug
: a synthetic drug created (as by genetic engineering) to treat a particular medical condition especially by producing a specific effect on the body's biochemistry
Synthetic version of a controlled narcotic substance. Designer drugs usually are synthesized for the first time in an attempt to create a chemical whose molecular structure differs only slightly from that of some well-known controlled substance but whose effects are essentially the same. Because of the difference in molecular structure, the designer drug, unlike the controlled substance, ordinarily will not be specifically listed as illicit by law-enforcement organizations. Many designer drugs are manufactured in clandestine laboratories, often by amateurs; for this reason they are sometimes more dangerous than the drugs they are intended to replace. One of the best-known is MDMA (3,4- methylenedioxymethamphetamine), a variation of methamphetamine, popularly called Ecstasy. Nonnarcotic synthetic chemical compounds designed to interact with specific proteins and enzymes in order to combat disease also have been called designer drugs.