C21H20O2

tetrahydrocannabinol et`ra*hy`dro*can*nab"i*nol (t[e^]t`r[.a]*h[imac]`dr[-o]*k[a^]n*n[a^]b"[i^]n[add]l), n. (Chem. & Med.) A chemical substance ({C21H20O2}) which is produced by the hemp plant (Cannabis sativa), and is the physiologically active agent of dried preparations of that plant, called variously marijuana, hashish, ganja, hemp, etc.; also called {THC}. It causes the euphoric effect for which the preparations are smoked or chewed. It is used in medicine in a purified form as an antiemetic (an antinausea agent), especially in conjunction with chemotherapy of cancer. It occurs primarily as the [Delta]1-3,4-trans isomer, also called {[Delta]9-THC}, with small amounts of the [Delta]6-3,4-trans isomer detectable at about 1%. It is a controlled substance, classified as a hallucinogen, and its possession and distribution is illegal in almost all states of the United States. --MI11 [PJC]