Medical marijuana for cancer
Background
Potential Harms of Marijuana
Introduction
Review of Potential Medical Uses for Marijuana and Cannabinoids in Cancer
As more states pass laws legalizing marijuana for medical use, the need for accurate information regarding the therapeutic effects of marijuana grows.
To inform these choices, a review of the published peer‐reviewed literature regarding marijuana and cannabinoid pharmaceuticals was undertaken.
Marijuana
Cannabinoid Receptors and Cannabinoids
Pharmaceutical Forms of Cannabinoids
Methods
Nausea and Vomiting
Marijuana
Pharmaceuticals
Pain
Marijuana
Pharmaceuticals
Treatment of Poor Appetite and Weight Loss
Marijuana
Cannabinoids as Antineoplastic Agents
Cancer
Lung Problems
Neuropsychiatric
Other
Summary
This is not meant as a recommendation for the use (or not) of marijuana, or of the legal and regulatory policies surrounding such use.
Marijuana, the dried leaves of the Cannabis sativa plant, has long been used both recreationally and as a medicine.
Because marijuana is a Schedule I controlled substance, physicians and other health care professionals who write prescriptions for it can be prosecuted under federal law.
Marijuana can be used to make hashish and hash oil, which contain concentrated cannabinoids (cannabinoids are discussed below).
Cannabis sativa contains a number of chemical compounds, some of which are classified as cannabinoids.
Vaporization has become an alternative to smoking as a means of inhaling marijuana.
THC is often called the major psychoactive component of marijuana because it appears to be responsible for the feeling of “high” reported by consumers of marijuana.
CBD is another major cannabinoid found naturally in the marijuana plant.
Because marijuana is a Schedule I controlled substance, marijuana used for research must be obtained through the National Institute of Drug Abuse (NIDA).
Delta‐9‐tetrahydrocannabinol
THC is highly lipophilic and is water insoluble.
A human study of vaporization of marijuana found that this delivery method yielded similar plasma THC levels compared with marijuana smoking, with lower carbon monoxide levels
THC can also be administered via the oral mucosa.
THC crosses the placenta and can be found in small amounts in breast milk.
Cannabidiol
CBD is also highly lipophilic. The absorption and kinetics of CBD from inhaled marijuana smoke have been described as being similar to those of THC.
in terms of peak plasma level and area under the curve, is increased if the oral mucosal spray is administered during a fed state.
Two cannabinoids are approved by the FDA and therefore can be legally prescribed in the United States according to federal law.
A phase 2 clinical trial of this drug in patients with schizophrenia is currently ongoing
To augment the PubMed search, the reference sections from review articles, meta‐analyses, and practice guidelines were reviewed to find additional clinical trials.
A search of PubMed found only 2 studies of smoked marijuana in the treatment of CINV.
The efficacy of oral THC in patients with CINV has been demonstrated in a number of studies of dronabinol.
The efficacy of nabilone in patients with CINV has also been explored in a number of studies. Many of these studies used a crossover design.
Administering nabilone in combination with dexamethasone was found to be superior to nabilone alone in the treatment of CINV.
A few studies to date have explored the effects of smoked marijuana on experimentally induced pain.
Studies of smoked marijuana in patients with pain that was not experimentally induced have concentrated on those with neuropathic pain.
For neuropathic pain, the results of studies of nabiximols have been mixed.
Only a few studies using nabiximols to treat cancer pain have been published to date.
In a study of patients with rheumatoid arthritis, nabiximols was found to improve pain and sleep quality better than placebo.
THC when given intravenously had variable effects on pain caused by dental extraction in a small study.
Nabilone improved pain from diabetic neuropathy in one placebo‐controlled study
The drug was not, however, helpful in the treatment of patients with acute postoperative pain, and in fact was linked to worsening of pain scores
Smoked marijuana caused an increase in caloric intake in studies of healthy volunteers.
Oral THC (as dronabinol) has been studied in the treatment of anorexia and wasting associated with HIV.
Dronabinol also improved food intake and decreased disturbed behavior in a small study of elderly patients with presumed Alzheimer disease.
Cannabinoid receptors have been found on cancer cells
and cannabinoids have shown evidence of antitumoral effects in vivo and in vitro in preclinical studies
Because smoked marijuana contains carcinogens, it does have the potential to cause cancer.
Although one case‐control study did show a link between marijuana smoking and incidence of head and neck cancer,
For lung cancer, a case‐control study found no link to marijuana smoking after adjustment for confounders such as cigarette smoking
There are no published studies of oral marijuana ingestion and cancer risk, nor are there any studies of vaporized marijuana and cancer risk.
Marijuana smoking can cause injury to the large airways and an increase in the symptoms of chronic bronchitis.
However, these effects subside after discontinuation of use, and there is no clear link between smoking marijuana and the development of chronic obstructive pulmonary disease
Studies have found acute effects of marijuana that include a reduction in performance at tests measuring memory, attention, reaction time, tracking, and motor function,
Although marijuana intoxication often leads to a feeling of euphoria, some individuals experience feelings of anxiety and/or paranoia, with hallucinations and other psychotic symptoms also being described.
Similar to other intoxicants, marijuana can impair driving skills and increase the risk of motor vehicle accidents.
In one study, women who used marijuana during pregnancy were more likely to have a stillbirth.
Both cannabis and cannabinoid pharmaceuticals can be helpful for a number of problems, including many affecting patients with cancer.
Given the problems with confounding and potential recall bias in case‐control studies examining cancer outcomes, these outcomes may be better examined through prospective cohort studies.
However, because marijuana smoke contains toxins and carcinogens, vaporization may be preferable as a way to inhale because it has less potential for harm.