| Occurrence | Marijuana is grown wild and is cultivated throughout the world. |
| Uses | Marijuana has been used for recreation. Dronabinol, which contains cannabis, is used to treat anorexia in appetite loss associated with AIDS and for cancer chemotherapy induced nausea. It is also helpful to reduce intraocular pressure in glaucoma. |
| Indications | The hemp plant, or cannabis (Cannabis sativa), continues
to be the most frequently abused illicit substance in
America. The dried leaves and flowering tops of the
plant are referred to as marijuana, and it is typically
smoked in pipes or rolled as cigarettes. It also may be
consumed in baked goods. Hashish is a solid black
resinous material obtained from the leaves of the plant
and is usually smoked in a pipe. |
| Definition | Its principle, tetrahydrocannabinol, can be made syn-
thetically. |
| Hazard | A mild hallucinogen. Sale is illegal in U.S.
Use: Medicine, ophthalmology (treatment of glau-
coma). |
| Mechanism of action | A cannabinoid receptor identified in the brain of several
species, including humans, is termed CB1. It is one
of the most abundant receptors in the CNS, and its distribution
within the brain reflects the pharmacological
effects produced by △9-THC. High receptor densities in
the extrapyramidal motor system and the cerebellum
are consistent with the actions of cannabinoids on many
forms of movement.The effects of cannabinoids on cognition
and memory may be due to the relatively dense
receptor populations in the hippocampus and cortex.
The presence of cannabinoid receptors in the ventromedial
striatum and nucleus accumbens suggests an association
with dopamine neurons hypothesized to mediate
brain reward. |
| Side effects | Marijuana is unique among drugs of abuse in that there
have been no credible reports of fatal overdose. The most prominent effect of acute marijuana use is intoxication,
which can impair the cognitive and motor skills
needed to complete complex tasks. Anxiety and panic
reactions are occasionally reported in inexperienced
users or following use of large quantities of marijuana.
9-THC causes its greatest effects on short-term memory,
as measured in free-recall tasks.Marijuana does not
affect the retrieval of previously learned facts. In contrast
to alcohol, there is no residual hangover from a
single use of high quantities of marijuana.
Heavy marijuana smoking produces bronchitis, and
some individuals have evidence of precancerous lung
conditions. However, definitive evidence of the relationship
between marijuana smoking and the incidence
of lung cancer is lacking. |