Medical marijuana - a basic scientific view
Medical cannabis or medical marijuana can refer to the use of the cannabis plant and its parts to treat diseases or improve symptoms. Scientific study of the chemicals in marijuana, called cannabinoids, has led to the United States of America (USA) Food and Drugs Authority’s (FDA’s) approved medications that contain cannabinoid chemicals in a pill form.
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Composition of marijuana
The cannabis plant contains more than 400 different chemicals, of which about 70 are cannabinoids. In comparison, typical pharmaceutically approved medications contain one or two chemicals. A 2014 review stated that the variations in the ratio of cannabidiol (CBD) to tetrahydrocannabinol (THC) in botanical and pharmaceutical preparations determine the therapeutic versus psychoactive effects.
Route of administration
Medical cannabis can be administered using a variety of methods, including liquid tinctures, vapourising or smoking dried buds, eating cannabis edibles, taking capsules, using lozenges, dermal patches or oral/dermal sprays. Synthetic cannabinoids are available as prescription drugs in countries such as USA, Canada, and New Zealand. Examples of such drugs are dronabinol and nabilone. Cannabinoid receptors have also been found in the skin making it a route of administration as topical marijuana for pain and inflammation.
Medical physiology of cannabis
THC is absorbed by the body much more slowly after oral intake (eating or drinking) and has a lower bio-availability of four to 12 per cent because of the poorer absorption catabolism (breakdown into simpler substances) in the liver. The fact is that the inactive tetrahydrocannabinolidic acid in natural cannabis products cannot be transformed into psychoactive delta-9-THC unless they are heated first, as is the case when it is smoked.
Medical marijuana for children
Some studies suggest medical marijuana may help relieve seizures in children with hard-to-treat epilepsy. A type of medical marijuana known as Charlotte's Web may help children without getting them high, because the strain has very little THC.
Nausea and vomiting
Medical cannabis is somewhat effective in chemotherapy-induced nausea and vomiting (CINV) and may be a reasonable option for those who do not improve following preferential treatment. Comparative studies have found cannabinoids to be more effective than some conventional anti-emetics such as prochlorperazine, promethazine and metoclopramide in controlling CINV, but these are used less frequently because of side effects such as dizziness, dysphoria and hallucinations.
Dementia
Cannabinoids have been proposed to have the potential for lessening the effects of Alzheimer's disease. A 2012 review of the effect of cannabinoids on brain ageing found that clinical evidence regarding their efficacy as therapeutic tools is either inconclusive or still missing. A 2009 Cochrane review said the one small randomised controlled trial that assessed the efficacy of cannabinoids in the treatment of dementia had poorly presented results and did not provide sufficient data to draw any useful conclusions.
Diabetes
There is emerging evidence that CBD may help slow cell damage in diabetes mellitus type one. There is a lack of meaningful evidence on the effects of medical cannabis used on people with diabetes; a 2010 review concluded that the potential risks and benefits for diabetic patients remain unquantified.
Epilepsy, other neurological problems and post-traumatic stress disorder
The efficacy of cannabis in treating neurological problems, including multiple sclerosis, epilepsy and movement problems, is not clear. Studies of the efficacy of cannabis for treating multiple sclerosis (MS) have produced varying results. The combination of THC and CBD extracts give subjective relief of spasticity, though objective post-treatment assessments do not reveal significant changes. Evidence also suggests that oral cannabis extract is effective for reducing patient-centred measures of spasticity.
Glaucoma
In 2009, the American Glaucoma Society noted that while cannabis could help lower intraocular pressure, it recommended against its use because of its side effects and short duration of action, coupled with a lack of evidence that its use altered the course of glaucoma.
Tourette syndrome
A 2007 review of the history of medical cannabis said cannabinoids showed potential therapeutic value in treating Tourette syndrome (TS). A 2005 review said controlled research on treating TS with dronabinol showed that the patients taking the pill had a beneficial response without serious adverse effects; a 2000 review said other studies had shown that cannabis had no effects on tics and increased the individual’s inner tension. A 2009 Cochrane review examined the two controlled trials to date using cannabinoids of any preparation type for the treatment of tics or Tourette syndrome TS (Muller -Vahl 2002, and Muller -Vahl 2003).
Anorexia nervosa
Cannabinoids have been proposed for the treatment of primary anorexia nervosa, but have no measurable beneficial effect. The authors of a 2003 paper argued that cannabinoids might have useful future clinical applications in treating digestive diseases. Laboratory experiments have shown that cannabinoids found in marijuana may have analgesic and anti-inflammatory effects.
Adjunct of cancer therapy
Laboratory experiments have suggested that cannabis and cannabinoids have anti-carcinogenic and anti-tumour effects, including a potential effect on breast and lung cancer cells. The National Cancer Institute reports that as of November 2013, there had been no clinical trials on the use of cannabis to treat cancer in people and there was only one small study using delta-9-THC that reported potential anti-tumoral activity.
Pain
Cannabis appears to be somewhat effective for the treatment of chronic pain, including pain caused by neuropathy and possibly that due to fibromyalgia and rheumatoid arthritis. A 2009 review states that it is unclear if the benefits are greater than the risks, while a 2011 review considered it generally safe for this use. In palliative care, the use appears safer than that of opioids. A 2015 meta-analysis found that inhaled medical cannabis was effective in reducing neuropathic pain in the short term for one in five to six patients.
Central nervous system
At a low to moderate dose, cannabis produces a largely pleasant feeling of relaxed euphoria, perhaps even with dreamy elements, which may be accompanied by heightening or alteration of the senses.
Cannabis and the brain
Employing modern brain imaging technologies such as the computed tomography (CAT) scan, magnetic resonance imaging (MRI), electro encephalogram (EEG) etc., researchers have found no evidence of brain damage in human cannabis users, even in subjects smoking an average of nine cannabis cigarettes per day. Brain wave patterns of chronic cannabis users and non-users produced by standard electroencephalographic (EEG) tests cannot be distinguished by visual examination.
Cognitive effects of cannabis
There is some clinical and experimental evidence, however, that the long-term use of cannabis may produce more subtle cognitive impairment in the higher cognitive functions of memory, attention, organisation and the integration of complex information, but the existence of a naturally occurring cannabinoid-like substance in the human brain (anandamide) signifies that this substance plays some role in our normal functioning. It has been suggested that anandamide may play a role in movement or motor control, in sleep and in the modulation of attention.
Psychotic disorders
There is suggestive evidence that large doses of THC can produce an acute psychosis in which confusion, amnesia, delusions, hallucinations, anxiety, agitation and hypomanic (mild mania without much change in behaviour) symptoms predominate.
Amotivational syndrome
It is exceptionally difficult, if not impossible, to establish a direct and exclusive causality between speculative consequences of chronic cannabis use and the drug itself. For example, studies attempting to link dropping out of school at an early age with cannabis use have tended to show that it was in fact the family background, the child's relationship with parents during the school years, social values, etc. which led the child to stop going to school and not smoking of cannabis.
Effects of cannabis on appetite
In a study by Foltrin et.al, subjects smoked placebo or active cannabis twice a day in their private rooms and twice a day in their social areas. Smoking active cannabis cigarettes increased food intake during both the private and social periods and greatest rate of change in caloric intake occurred during the social periods for most subjects.
Until better measures have been developed to investigate the subtleties of dysfunction produced by chronic cannabis use, cannabis can be viewed as posing a lower level threat to cognitive function than other psychoactive substances such as alcohol.