Medical marijuana (cannabis)

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Kraft B. Is there any clinically relevant cannabinoid-induced analgesia? Pharmacology. 2012;89(5-6):237-46

Medical marijuana (also marijuana / marihuana, and medical cannabis, or popularly hemp, medical pot or simply pot) refers to the use of cannabis and its associated cannabinoids (tetrahydrocannabinol (THC) and cannabidiol (CBD)) to treat pain, epilepsy, headaches and other ailments. Marijuana, hemp and cannabis are common names for plants of the genus Cannabis. The term "hemp" is used for various strains of Cannabis grown for industrial, nondrug usage. Cannabis sativa (Latin) is the variety grown for such purposes, while Cannabis sativa subsp. indica generally has poor fiber quality and is used to produce recreational and medicinal drugs. The major difference between the two types of plants is the appearance and the amount of delta-9-tetrahydrocannabinol (THC).

The two most commonly studied constituents of Cannabis sativa are a psychoactive component, THC, and a nonpsychoactive component, cannabidiol (CBD). Cannabinoids are active chemicals in Cannabis that cause drug-like effects throughout the body, including the central nervous system and the immune system. Available studies investigating Cannabis sativa have evaluated these compounds both alone and in combination. Commercially available products include dronabinol (Marinol®), nabilone (Cesamet®), THC, and CBD (Sativex®). Both THC and CBD have been shown in clinical trials to reduce chronic pain in patients unresponsive to standard analgesics and narcotics. Cannabis-based products such as Sativex® (oromucosal spray) are widely-prescribed to treat neuropathic pain, multiple sclerosis spasticity and cancer pain. The use of marijuana in non-cancer related (neuropathic) pain is the subject of clinical trials and systematic reviews worldwide. The active components in marijuana act on cannabinoid receptors in the central nervous system (CNS) and immune cells. Marijuana is approved for medicinal purposes in many European countries and Canada, but is still controversial.

Medical cannabis has several potential beneficial effects. Cannabinoids can serve as appetite stimulants, antiemetics, antispasmodics, and have some analgesic effects. In 2014, the range of medical and legal issues associated with the use of medical marijuana is why it continues to be controversial in medicine.

History of marijuana

  • Cannabis may have been cultivated in Asia as long as ten thousand years ago. It was certainly cultivated in China by 6000 BC
  • 4000 BC in China, hemp was used in the making of textiles
  • 3000 BC, there is evidence cannabis was first used in Chinese medicine
  • the nonpsychoactive variants of cannabis were cultivated in Asia during the Stone Age
  • 500 BC, Europeans introduce the plant, probably in the northern part of the continent
  • In the 1600s, settlers of the Americas were said to have observed Indian tribes cultivating the plant
  • By 1840, in America, medicinal preparations with a Cannabis base are available; hashish is available in Persian pharmacies
  • By 1850, cannabis was one of the largest crops grown in America; in England, Queen Victoria used it for menstrual pain
  • Early 1900s, the US Pure Food and Drug Act is passed, regulating products containing alcohol, opiates, cocaine, cannabis, etc.
  • 1920s and 30s, restrictions are put on the use of cannabis making it illegal in China and the US
  • Early 1970s, Nixon appointed a commission to legalize cannabis, but nothing comes of it
  • 1975 a "Compassionate Use" program is set up in the US; in the 90s and early 21st century US and Britain establish lower penalties
  • 2001 Canada is the first country to offer medical marijuana to those in need
  • Today, there are almost 10,000 people in Health Canada's MMAR program

Marijuana and pain

The use of marijuana in treating pain, particularly chronic pain, is the subject in Martin-Sanchez' 2009 Systematic review and meta-analysis of cannabis treatment for chronic pain. The review concludes that cannabis is moderately efficacious for treating chronic pain but its risk (and its potentially serious harms) offset treatment benefit. The conclusions reflect the evidence presented but the paper may not be completely reliable, as it is compromised by an incompletely reported review process and citing trials of less than optimal quality.

Since 2009, Cannabinoids have been reported to reduce chronic pain in patients not fully responsive to other analgesics including narcotics. Cannabis-based products like Sativex®, an oromucosal spray, are used to treat pain, including neuropathic pain, multiple sclerosis spasticity and cancer pain. The use of cannabis for neuropathic pain is the topic of several reviews. The active components exert action on cannabinoid receptors in the central nervous system and immune cells. Sativex® is approved in Canada, and numerous European countries; in the US, it is an investigational drug being developed as an adjunct analgesic in patients with cancer-related pain. Other cannabis-based products such as dronabinol (Marinol®), which are U.S. Food and Drug Administration (FDA) approved, are being studied for use in treating various types of pain.

In human research from 2003, in patients with chronic pain 2.5-120mg in divided doses has been used for two weeks. Doses of Sativex® include self-administration based on titration. Self-titration doses were up to 48 sprays daily, and after 1-2 weeks 10-15 sprays daily, or 4-8 sprays of Sativex®, eight being the maximum one-time dose within a three-hour period. According to a 2009 meta-analysis, cannabinoids were administered via oral capsules and oromucusal sprays as THC, benzopyranoperidine (BPP), cannabidiol (CBD), nabilone, dronabinol or synthetic nitrogen THC analogs (NIB). Dosing ranged from 2.5mg to 20mg for an average duration of 25 days. According to a 2009 systematic review, cannabis-based medicines, nabilone, dronabinol, smoked cannabis, and ajulemic acid have been used in doses of nabilone of 0.25-2mg daily; the dose of smoked cannabis was 1-9.4%; and the dose of dronabinol was 10-20mg daily for durations ranging from six hours to six weeks (six hours to 14 days for studies investigating smoking cannabis, 4-6 weeks for nabilone, one day to four weeks for dronabinal, 1-6 weeks for cannabis-based medicine, and one week for ajulemic acid.

According to a 2010 systematic review, for patients suffering from painful HIV-associated sensory neuropathy, cannabis was smoked 3-4 times daily for five days. Evidence of efficacy seemed to be for capsaicin 8%, smoked cannabis and rhNGF. However, rhNGF was clinically unavailable, and smoked cannabis was not considered on par nor could it be recommended in this study.

Other issues in literature

In 2011, a narrative review by Lynch et al (2011) of the literature around cannabinoids looked at a number of studies and routes of administration of marijuana: smoked cannabis, oromucosal extracts of cannabis based medicine, nabilone, dronabinol and a novel THC analogue. Various chronic pain conditions were studied such as neuropathic pain, fibromyalgia, rheumatoid arthritis and mixed chronic pain. Fifteen (15) of the eighteen trials that met the inclusion criteria demonstrated a significant analgesic effect of cannabinoid as compared with placebo and several reported significant improvements in sleep. There were no serious adverse effects. Adverse effects most commonly reported were generally well-tolerated, mild to moderate in severity and led to withdrawal in only a few cases. The researchers concluded that there is evidence cannabinoids are effective in treating neuropathic pain with some evidence of efficacy in fibromyalgia and rheumatoid arthritis.

In 2010, a Cochrane Collaboration review stated that cannabinoids were "probably effective" in treating chemotherapy-induced nausea in children but came with a significant side-effects profile (i.e., drowsiness, dizziness, altered moods and increased appetite). Some less common side-effects included "ocular problems, orthostatic hypotension, muscle twitching, pruritis, vagueness, hallucinations, lightheadedness and dry mouth". According to a 2009 systematic review, chronic use of cannabis is associated with psychiatric, respiratory, cardiovascular, and bone toxicities. Adverse events associated with cannabis include myocardial infarction and arrhythmias. Evidence supporting arteritis associated with cannabis is lacking. Authors indicate that the clinical and pathological features of arteritis are the same as those of thromboangiitis obliterans, which is associated with use of tobacco, and tobacco usage is prevalent in subjects with arteritis. Specific details for adverse events related to cannabis are lacking though one study discusses heart problems that may be associated with cannabis use in patients with existing heart disease.

Adverse Effects

Adverse side effects of cannabinoids may include:

  • Rapid beating of the heart
  • Low blood pressure
  • Muscle relaxation
  • Bloodshot eyes
  • Slowed digestion and movement of food by the stomach and intestines
  • Dizziness
  • Depression
  • Hallucinations, even paranoia

Important websites




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