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Medical cannabis, medicinal cannabis or medical marijuana ( MMJ) refers to cannabis products and cannabinoid that are prescribed by for their patients. The use of cannabis as medicine has a long history, but has not been as rigorously tested as other medicinal plants due to legal and governmental restrictions, resulting in limited research to define the safety and efficacy of using cannabis to treat diseases.
There is mixed and inconclusive evidence on the benefits of cannabis-based medicines, frequent mild adverse effects, and generally low-to-moderate quality of evidence. Cannabis-based medicines may offer modest relief for Chronic pain, especially Neuropathic pain, pain and slight improvements in function and sleep in chronic pain patients, but evidence is limited and inconsistent; mild harms may outweigh the benefit and placebo effects may influence trial outcomes.
Short-term use increases the risk of minor and major adverse effects. Common side effects include dizziness, feeling tired, vomiting, and . Long-term effects of cannabis are not clear. Concerns include memory and cognition problems, risk of addiction, schizophrenia in young people, and the risk of children taking it by accident.
Many cultures have used cannabis for therapeutic purposes for thousands of years. Some American medical organizations have requested removal of cannabis from the list of Schedule I controlled substances, emphasizing that rescheduling would enable more extensive research and regulatory oversight to ensure safe access. Others oppose its legalization, such as the American Academy of Pediatrics. Countries that allow the medical use of whole-plant cannabis include Argentina, Australia, Canada, Chile, Colombia, Germany, Greece, Israel, Italy, the Netherlands, Peru, Poland, Portugal, Spain, and Uruguay. In the United States, 38 states and the District of Columbia have legalized cannabis for medical purposes, beginning with the passage of California's Proposition 215 in 1996.
A cannabis plant includes more than 400 different chemicals, of which about 70 are . In comparison, typical government-approved medications contain only one or two chemicals. The number of active chemicals in cannabis is one reason why treatment with cannabis is difficult to classify and study.
A 2014 review stated that the variations in ratio of CBD-to-THC in botanical and pharmaceutical preparations determines the therapeutic vs psychoactive effects (CBD attenuates THC's psychoactive effects) of cannabis products.
Low quality evidence suggests its use for reducing antiemetic during chemotherapy, improving appetite in HIV/AIDS, improving sleep, and improving in Tourette syndrome. When usual treatments are ineffective, have also been recommended for anorexia, arthritis, glaucoma, and migraine.
It is unclear whether American states might be able to mitigate the adverse effects of the opioid epidemic by prescribing medical cannabis as an alternative pain management drug.
Cannabis should not be used in pregnancy.
Short-term use of oral or sublingual cannabis, particularly high-THC synthetic or comparable-THC extracted products, may modestly reduce chronic pain but increases risks of dizziness, sedation, and other adverse effects, with limited evidence on long-term outcomes.
Placebo contribute to pain reduction in cannabinoid clinical trials, and while media attention is high, it does not directly correlate with clinical outcomes but may influence future expectations and trial results.
A 2016 Cochrane review said that cannabinoids were "probably effective" in treating chemotherapy-induced nausea in children, but with a high side-effect profile (mainly drowsiness, dizziness, altered moods, and increased appetite). Less common side effects were "ocular problems, orthostatic hypotension, muscle twitching, pruritus, vagueness, hallucinations, lightheadedness and dry mouth".
The relationship between cannabis use and anxiety symptoms is complex, and while some users report relief, the overall evidence from observational studies and clinical trials remains inconclusive.
Cannabis use, especially at high doses, is associated with a higher risk of psychosis, particularly in individuals with a genetic predisposition to psychotic disorders like schizophrenia. Some studies have shown that cannabis can trigger a temporary psychotic episode, which may increase the risk of developing a psychotic disorder later.
The impact of cannabis on depression is less clear. Some studies suggest a potential increase in depression risk among adolescents who use cannabis, though findings are inconsistent across studies.
A 2007 meta analysis concluded that cannabis use reduced the average age of onset of psychosis by 2.7 years relative to non-cannabis use. A 2005 meta analysis concluded that adolescent use of cannabis increases the risk of psychosis, and that the risk is dose-related. A 2004 literature review on the subject concluded that cannabis use is associated with a two-fold increase in the risk of psychosis, but that cannabis use is "neither necessary nor sufficient" to cause psychosis. A French review from 2009 came to a conclusion that cannabis use, particularly that before age 15, was a factor in the development of schizophrenic disorders.
The most psychoactive cannabinoid found in the cannabis plant is tetrahydrocannabinol (or delta-9-tetrahydrocannabinol, commonly known as THC). Other cannabinoids include delta-8-tetrahydrocannabinol, cannabidiol (CBD), cannabinol (CBN), cannabicyclol (CBL), cannabichromene (CBC) and cannabigerol (CBG); they have less psychotropic effects than THC, but may play a role in the overall effect of cannabis. The most studied are THC, CBD and CBN.
CB1 and CB2 are the primary cannabinoid receptors responsible for several of the effects of cannabinoids, although other receptors may play a role as well. Both belong to a group of receptors called G protein-coupled receptors (GPCRs). CB1 receptors are found in very high levels in the brain and are thought to be responsible for psychoactive effects. CB2 receptors are found peripherally throughout the body and are thought to modulate pain and inflammation.
Inhaled and vaporized THC have similar absorption profiles to smoked THC, with a bioavailability ranging from 10 to 35%. Oral administration has the lowest bioavailability of approximately 6%, variable absorption depending on the vehicle used, and the longest time to peak plasma levels (2 to 6 hours) compared to smoked or vaporized THC.
Similar to THC, CBD has poor oral bioavailability, approximately 6%. The low bioavailability is largely attributed to significant first-pass metabolism in the liver and erratic absorption from the gastrointestinal tract. However, oral administration of CBD has a faster time to peak concentrations (2 hours) than THC.
Due to the poor bioavailability of oral preparations, alternative routes of administration have been studied, including sublingual and rectal. These alternative formulations maximize bioavailability and reduce first-pass metabolism. Sublingual administration in rabbits yielded bioavailability of 16% and time to peak concentration of 4 hours. Rectal administration in monkeys doubled bioavailability to 13.5% and achieved peak blood concentrations within 1 to 8 hours after administration.
Next, 11-OH-THC is metabolized in the liver into 11-COOH-THC, which is the second metabolic product of THC. 11-COOH-THC is not psychoactive.
Ingestion of edible cannabis products lead to a slower onset of effect than the inhalation of it because the THC travels to the liver first through the blood before it travels to the rest of the body. Inhaled cannabis can result in THC going directly to the brain, where it then travels from the brain back to the liver in recirculation for metabolism. Eventually, both routes of metabolism result in the metabolism of psychoactive THC to inactive 11-COOH-THC.
CBD is hydroxylated by P450 liver enzymes into 7-OH-CBD. Its metabolites are products of primarily CYP2C19 and CYP3A4 activity, with potential activity of CYP1A1, CYP1A2, CYP2C9, and CYP2D6. Similar to delta-9-THC, a majority of CBD is excreted in feces and some in the urine. The terminal half-life is approximately 18–32 hours.
The US Food and Drug Administration (FDA) has not approved smoked cannabis for any condition or disease, as it deems that evidence is lacking concerning safety and efficacy. The FDA issued a 2006 advisory against smoked medical cannabis stating: "marijuana has a high potential for abuse, has no currently accepted medical use in treatment in the United States, and has a lack of accepted safety for use under medical supervision."
The Ebers Papyrus () from Ancient Egypt describes medical cannabis. The ancient Egyptians used hemp (cannabis) in suppositories for relieving the pain of .
Surviving texts from ancient India confirm that cannabis' psychoactive properties were recognized, and doctors used it for treating a variety of illnesses and ailments, including insomnia, headaches, gastrointestinal disorders, and pain, including during childbirth.
The Ancient Greeks used cannabis to dress wounds and sores on their horses, and in humans, dried leaves of cannabis were used to treat nose bleeds, and cannabis seeds were used to expel tapeworms.
In the medieval Islamic world, Islamic medicine made use of the diuretic, antiemetic, antiepileptic, anti-inflammatory, analgesic and antipyretic properties of Cannabis sativa, and used it extensively as medication from the 8th to 18th centuries.
Widely cultivated strains of cannabis, such as "Afghani" or "Hindu Kush", are indigenous to the Pakistan and Afghanistan regions, while "Durban Poison" is native to Africa. There are approximately 16 landrace strains of cannabis identified from Pakistan, Jamaica, Africa, Mexico, Central America and Asia. (2025). 9781429219617, W.H. Freeman and Company. ISBN 9781429219617
The use of cannabis in medicine began to decline by the end of the 19th century, due to difficulty in controlling dosages and the rise in popularity of synthetic and opium-derived drugs. Also, the advent of the hypodermic syringe allowed these drugs to be injected for immediate effect, in contrast to cannabis which is not water-soluble and therefore cannot be injected.
In the United States, the medical use of cannabis further declined with the passage of the Marihuana Tax Act of 1937, which imposed new regulations and fees on physicians prescribing cannabis. Cannabis was removed from the U.S. Pharmacopeia in 1941, and officially banned for any use with the passage of the Controlled Substances Act of 1970.
Cannabis began to attract renewed interest as medicine in the 1970s and 1980s, in particular due to its use by cancer and AIDS patients who reported relief from the effects of chemotherapy and Cachexia. In 1996, California became the first U.S. state to legalize medical cannabis in defiance of federal law. In 2001, Canada became the first country to adopt a system regulating the medical use of cannabis.
Countries that have legalized the medical use of cannabis include Argentina, Australia, Brazil, Canada, Chile, Colombia, Costa Rica, Croatia, Cyprus, Czech Republic, Finland, Germany, Greece, Israel, Italy, Jamaica, Lebanon, Luxembourg, Malta, Morocco, the Netherlands, New Zealand, North Macedonia, Panama, Peru, Poland, Portugal, Rwanda, Sri Lanka, Switzerland, Thailand, the United Kingdom, and Uruguay. Other countries have more restrictive laws that allow only the use of isolated cannabinoid drugs such as Sativex or Epidiolex. Countries with the most relaxed policies include Canada, the Netherlands, Thailand, and Uruguay, where cannabis can be purchased without need for a prescription. In Mexico, THC content of medical cannabis is limited to one percent. In the United States, the legality of medical cannabis varies by state.
However, in many of these countries, access may not always be possible under the same conditions.
Cannabis and cannabis resin are classified as a Schedule I drug under the Single Convention treaty, meaning that medical use is considered "indispensible for the relief of pain and suffering" but that it is considered to be an addictive medication with risks of abuse. Countries have an obligation to provide access and sufficient availability of drugs listed in Schedule I for the purposes of medical uses.
Prior to December 2020 cannabis and cannabis resin were also included in Schedule IV, a more restrictive level of control, which is for only the most dangerous drugs such as heroin and fentanyl. They were removed after an independent scientific assessment by the World Health Organization in 2018-2019.
Member nations of the UN Commission on Narcotic Drugs voted 27–25 to remove it from Schedule IV on 2 December 2020, following a World Health Organization recommendation for removal in January 2019.
In the US, the FDA has approved two oral cannabinoids for use as medicine in 1985: dronabinol (pure delta-9-THC; brand name Marinol) and nabilone (a synthetic neocannabinoid; brand name Cesamet). In the US, they are both listed as Schedule II, indicating high potential for side effects and addiction.
Almost 70% of medical cannabis is exported from the United Kingdom, according to a 2017 United Nations report, with much of the remaining amount coming from Canada and the Netherlands.
Organizations that oppose the legalization of medical cannabis include the American Academy of Pediatrics (AAP) and American Psychiatric Association. However, the AAP also supports rescheduling for the purpose of facilitating research.
The American Medical Association and American College of Physicians do not take a position on the legalization of medical cannabis, but have called for the Schedule I classification to be reviewed. The American Academy of Family Physicians and American Society of Addiction Medicine also do not take a position, but do support rescheduling to better facilitate research. The American Heart Association says that "many of the concerning health implications of cannabis include cardiovascular diseases" but that it supports rescheduling to allow "more nuanced ... marijuana legislation and regulation" and to "reflect the existing science behind cannabis". The American Cancer Society and American Psychological Association have noted the obstacles that exist for conducting research on cannabis, and have called on the federal government to better enable scientific study of the drug.
Cancer Research UK say that while cannabis is being studied for therapeutic potential, "claims that there is solid "proof" that cannabis or cannabinoids can cure cancer is highly misleading to patients and their families, and builds a false picture of the state of progress in this area".
Nabiximols is the generic name (but not recognized as an INN) of a mixture of Cannabidiol and Dronabinol. Its most common form is the oromucosal spray derived from two strains of Cannabis sativa and containing THC and CBD traded under the brand name Sativex®. It is not approved in the United States, but is approved in several European countries, Canada, and New Zealand as of 2013.
| Nabilone | Cesamet | U.S., Canada | Antiemetic (treatment of nausea or vomiting) associated with chemotherapy that has failed to respond adequately to conventional therapy |
| Dronabinol | Marinol | ||
| Syndros | U.S. | Anorexia associated with AIDS–related weight loss | |
| Nabiximols | Sativex | Canada, New Zealand, majority of the EU | Limited treatment for spasticity and neuropathic pain associated with multiple sclerosis and intractable cancer pain. |
As an antiemetic, these medications are usually used when conventional treatment for nausea and vomiting associated with cancer chemotherapy fail to work.
Nabiximols is used for treatment of spasticity associated with MS when other therapies have not worked, and when an initial trial demonstrates "meaningful improvement". Trials for FDA approval in the US are underway. It is also approved in several European countries for overactive bladder and emesis. When sold under the trade name Sativex as a mouth spray, the prescribed daily dose in Sweden delivers a maximum of 32.4 mg of THC and 30 mg of Cannabidiol; mild to moderate dizziness is common during the first few weeks.
Relative to inhaled consumption, peak concentration of oral THC is delayed, and it may be difficult to determine optimal dosage because of variability in patient absorption.
In 1964, Albert Lockhart and Manley West began studying the health effects of traditional cannabis use in Jamaicans communities. They developed, and in 1987 gained permission to market, the pharmaceutical "Canasol", one of the first cannabis extracts.
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