Cannabis sativa or marijuana has been used as medicine for a long time, but it has been illegal to possess marijuana since the Marihuana Tax Act of 1937 in the United States. The U.S. Drug Enforcement Administration lists marijuana and the cannabinoids it contains as being illegal to prescribe. Some states have now made marijuana legal, and physicians who authorize patients to use marijuana are protected from prosecution by doctor-patient privacy.
Marijuana can be smoked or taken by mouth as a tea or in baked goods. It has some of the same toxic contents as tobacco smoke. Some are classed as carcinogens, such as arsenic, benzene, cadmium, formaldehyde, and lead. Vaporizing and inhaling marijuana releases large amounts of cannabinoids and little of other contents (such as carbon monoxide). It has become an alternative to smoking.
Cannabinoids are chemicals which attach to the cannabinoid receptors on cells of the brain. This includes cannabinoids which are found in marijuana and some which are not. The receptors are called CB1 (mainly in the nervous system) and CB2 (mainly in the immune system). Endocannabinoids are chemicals found in and produced by the body which can attach to the cannabinoid receptors.
Of the approximately 60 cannabinoids in marijuana, the main ones are THC (9-tetrahydrocannabinoid) and CBD (cannabidiol}. THC is mainly responsible for the “high”, and CBD may relieve anxiety, treats seizures, and relieves pain. Over time the THC content has increased in marijuana, and the CBD content has declined, possibly due to breeding. Absorption of cannabinoids is rapid after inhalation, but “slow and erratic” after eating baked goods and they are degraded by stomach acids. THC crosses the placenta, and small amounts may be found in breast milk. Absorption of CBD is similar to that of THC.
Two synthetic cannabinoids (dronabinol and nabilone) can be legally prescribed for nausea, vomiting, and weight loss associated with HIV. Nabiximols is a whole-plant extract with a THC/CBD ratio of 1.08/1.00. It is used for pain, and also for spastisity from multiple sclerosis.
This article is a review of research done of marijuana in cancer symptoms, such as nausea, vomiting, loss of appetite, and weight loss. Few studies have been done, but there is evidence that both smoked and oral marijuana may relieve nausea and vomiting associated with methotrexate chemotherapy. In one study, patients preferred the placebo to dronabinol because of dronabinol’s side effects. Nabilone is hampered by central nervous system side effects, such as drowsiness, dizziness, low blood pressure, lightheadedness, euphoria, and hallucinations.
Pain of nerve origin is most often studied, and smoked marijuana is found to be superior to placebo for pain. Nabiximols relieved pain of central nervous system origin in one study. Nabiximols relieved pain and improved sleep in patients with rheumatoid arthritis in another study. Dronabinol did not do much to relieve pain except for pain related to spastisity in multiple sclerosis. Smoked marijuana shows good results in cancer when smoked for poor appetite or nausea, but does not necessarily result in weight gain. Dronabinol gives variable results in cancer patients without much improvement.
Cannabinoid receptors have been found on cancer cells and cannabinoids have had some anticancer effects, in vivo, in vitro, and in preclinical studies of the following cancers: glioma, hepatocellular (liver), prostate, lung, cholangiocarcinoma, breast, and melanoma. There are current studies of cannabinoids in glioma and results are pending.
Many studies have been done of the risk of marijuana causing cancer without convincing results. Two studies have shown some increased risk of testicular cancer, but there is no clear connection between marijuana smoking and chronic obstructive pulmonary disease (COPD). Marijuana smokers show impaired memory,attention, and motor function 1 hour after smoking. For those eating marijuana time is about 2 hours. The impairment lasts for about 4 hours. Current heavy smokers can show cognitive impairment for up to 7 days.
CONCLUSION: Inhalation of marijuana is better for relieving symptoms of cancer than by oral use. However, because of the possibility of toxic exposures from smoking, vaporization may be the preferred form of use.
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