Taber's Medical Dictionary

marijuana, marihuana

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(mar″ĭ-wan′ă )

[Mexican Sp. marihuana, mariguana]
The dried flowering tops of Cannabis sativa, the hemp plant. Marijuana has many colloquial and street names, e.g., dope, ganja, Mary Jane, pot, and weed.
SEE: Cannabis sativa; SEE: tetrahydrocannabinol
Its active ingredient, delta-9-tetrahydrocannabinol (THC), may produce euphoria, alterations in mood and judgment, and changes in sensory perception, cognition, and coordination. Driving and machine-operating skills may be impaired. Users of marijuana have impaired short-term memory; memory deficits are transient, however, and return to normal within about a week of abstinence. Depending on the dose of the drug and the underlying psychological conditions of the user, marijuana may cause transient episodes of confusion, anxiety, or delirium. Its use may exacerbate mental illness, esp. schizophrenia. Long-term, relatively heavy use may be associated with behavioral disorders and a kind of ennui called the amotivational syndrome, but it is not known whether use of the drug is a cause or a result of this condition. Transient symptoms occur on withdrawal, indicating that the drug can lead to physical dependence. There has been considerable interest in the effects of marijuana on pregnancy and fetal growth, but substance abusers often abuse more than a single substance, making it difficult to evaluate the effects of individual substances on the outcome of pregnancy or fetal development.

There is no definitive evidence that prolonged heavy smoking of marijuana leads to impaired pulmonary function. The possibility that chronic marijuana use is associated with an increased risk of developing head and neck cancer exists, but it has not been proven.

Delta-9-tetrahydrocannabinol, also known as dronabinol, is approved for use in treating nausea and vomiting associated with cancer chemotherapy in patients who have failed to respond adequately to conventional antiemetic treatment, and treatment of anorexia associated with weight loss in patients with acquired immunodeficiency syndrome. Marijuana has also been approved for other medical uses in some states, although such use violates federal Drug Enforcement Administration standards.

Dronabinol is a controlled substance. Prescriptions are limited to the amount necessary for a single cycle of chemotherapy.

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