Cancers cannabis

Dronabinol (tetrahydrocannabinol), the active principle from cannabis and synthetic cannabinoids, nabilone and levonantradol are effective in treating nausea and vomiting in cancer chemotherapy. The mode of action is unclear but appears to involve cannabinoid CBi receptors. Cannabinoids have been shown to reduce acetylcholine release in the cortex and hippocampus, and have been suggested to inhibit medullary activity by a cortical action. Inhibition of prostaglandin synthesis and release of endorphins may also be involved in the antiemetic effect. A review of trials of dronabinol, nabilone or levonantradol concluded that while the cannabinoids were superior to placebo or dopamine receptor antagonists in controlling emesis... 

There is no conclusive evidence that moderate, long-term use of cannabis causes lasting damage to physical or mental health. However, it is probable that frequent inhalation of cannabis smoke over a period of years will contribute towards bronchitis and other respiratory disorders and possible cancers of the lung and parts of the digestive system. Risks are greater if cannabis is smoked with tobacco. 

The reduction of nausea in patients taking anti-cancer drug therapy is probably the most widely researched area for cannabis therapy. A number of these studies have shown that oral administration of isolated cannabinoids produce significant improvements, particularly for those patients who have failed to respond to standard antinausea treatments during chemotherapy (see Tortorice and O Connell, 1990 for a comprehensive review). Patients and oncologists have subjectively reported that smoked marijuana is as safe (in this patient group) and effective as isolated oral cannabinoids, but more systematic research trials are required. 

One of the major toxicity issues in cannabis consumption relates to the fact that it is most often smoked. Cannabis and tobacco smoke, apart from having different psychoactive constituents, are actually very similar in their composition (Hoffman et ai. 1975). Cannabis smoke is mutagenic, which gives it carcinogenic potential (Nahas and Latour 1992). Although no specific reports of lung cancer or emphysema from cannabis smoke exist, it is at least as harmful as tobacco smoke, containing three times as much tar and five times as much carbon monoxide (Wu et al. 1988). Cannabis smoke inflames the airways and reduces respiratory capacity. Airway obstruction and squamous metaplasias may also occur. 

Ungerleider JT, Andrysiak T, Fairbanks L, Goodnight J, Sarna G, Jamison K. (1982). Cannabis and cancer chemotherapy a comparison of oral delta-9-TFIC and prochlorperazine. Cancer. 50(4) 636-45. 

M. E. Lynch, and A. J. Clark Cannabis use for chronic non-cancer pain results of a prospective survey. Pain 2003 102(l-2) 211-216. 

The resin secreted by Cannabis indica and Cannabis sativa, varieties of hemp, is known variously as marijuana, hashish or bhang and is abused as a hallucinogenic drug. It appears however to have some beneficial properties and is currently under test as an antiemetic in cancer therapy. The secretion contains a number of interrelated oxygen heterocycles, some of which are shown in Scheme 281, which attempts to indicate their biosynthetic relationships (70MI22401). The cannabinoids are probably derived from a monoterpene unit based on p-menthane and 5-n-pentylresorcinol (olivetol), acting the part of a polyketide. 2,2-Dimethylchromene biosynthesis also requires the intervention of an isoprene fragment. 

The opium alkaloids codeine and morphine served as models for the synthesis of naloxone, an important analog used to treat and diagnose opiate addicts, and also led to the discovery of endogenous opioids (enkephalins and endorphins) (see Chapter 47). Similarly, A9-tetrahydro-cannabinol (THC), the component of Cannabis sativa responsible for the central nervous system (CNS) effect, has also been found to reduce nausea associated with cancer chemotherapy (see Chapter 18). 

A9-Tetrahydrocannabinol (A9-THC) is considered to be the predominant compound in preparations of C. sativa (marijuana, hashish, bhang) that is responsible for the central nervous system effects in humans. The recognized central nervous system responses to these preparations include alterations in cognition and memory, euphoria, and sedation. Potential therapeutic applications of cannabis preparations that are of either historical or contemporary interest include analgesia, attenuation of the nausea and vomiting of cancer chemotherapy, appetite stimulation, decreased intestinal motility of diarrhea, decreased bronchial constriction of asthma, decreased intraocular pressure of glaucoma, antirheumatic and antipyretic actions, and treatment of convulsant disorders. These effects have been reviewed recently (Howlett, 1995). 

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