Marijuana as Medicine: Is the Grass Looking Greener?
Marijuana. Smoking the substance may mellow the emotions, but talking about it often does just the opposite. For baby boomers, marijuana may be associated with memories of an idealistic youth movement, Vietnam War protests, and peace signs. For others, it stirs up fears of illicit drug use, addiction, and juvenile delinquency. But for many people with serious medical conditions such as cancer, ]]>AIDS]]> , and chronic pain, marijuana has become a symbol of hope for the relief of pain and suffering.
Hashing Over the History of Hemp
Marijuana ( Cannabis sativa L. ), also known as marihuana, Indian hemp, or hashish, is a member of the Cannabaceae or hemp family. The weedy plant, believed to have originated in India, has been cultivated for thousands of years. Ingested by smoking or eaten as a dried herb in various preparations, marijuana has been used around the world for its medicinal and mood-altering properties.
In the 1850s, hemp, grown primarily for manufacturing the rope used to rig sailing ships, was one of the largest agricultural crops grown in North America. Curiously, the use of marijuana as a mind-altering substance appears to have been relatively uncommon in the US until the early 20th century. In 1937, the US federal government prohibited the cultivation and use of marijuana, categorizing it as an illegal narcotic. In recent years, a movement has been underway in individual states to legalize the medicinal use of marijuana.
Marijuana contains more than 400 chemical components. Delta-9-tetrahydrocannabinol (delta THC) is believed to be the component most responsible for psychoactive effects, but the drug has other important constituents as well. Taken together, the active ingredients found in marijuana are known as cannabinoids. Today, scientists continue to evaluate the usefulness of marijuana and its components in medicine.
“Weeding” Through the Evidence
Current knowledge of the effects of marijuana comes from the following sources:
- Personal stories of people who have taken the drug
- Historical accounts of its use—some more than a thousand years old
- A limited number of clinical studies
- Scientific research on marijuana and its constituent components
In the 2000 report, Marijuana and Medicine , the Institute of Medicine presented an evidence-based analysis of the usefulness of marijuana and its components in the treatment of the following conditions. Here are some of their main findings:
People with cancer who use marijuana report that it helps reduce nausea and vomiting, increases appetite, relieves pain, and soothes anxiety. Some clinical studies indicate that marijuana is not as effective in treating these conditions as many available medications. But an editorial in the July 2001 issue of the British Medical Journal highlighted a number of studies indicating that cannabinoids were actually more effective than conventional drugs in preventing nausea and vomiting in people undergoing chemotherapy.
During the past decade, synthetic THC, known as ]]>dronabinol]]> (Marinol), has been used to treat nausea and vomiting in cancer patients. Researchers speculate that other cannabinoids or combinations of cannabinoids might be effective in people who respond poorly to THC. Majority of patients who used marijuana in the past say that Marinol has not been as effective in controlling their symptoms.
Pain is the most common symptom in people seeking medical assistance. Available evidence from a small number of animal and human studies suggest that cannabinoids may help reduce post surgical and chronic pain. However, due to limitations in the design of these studies, results are inconclusive.
Nerve damage, called ]]>peripheral neuropathy]]> , is a condition that affects people with HIV. Two randomized trials found that smoking cannabis helped relieve this nerve pain. ]]>*]]> People with HIV are also vulnerable to wasting syndrome (a substantial, involuntary loss of weight) and loss of appetite. Little has been published, though, about the effectiveness of marijuana for treating these conditions. Several placebo-controlled studies indicate that smoking marijuana stimulates appetite in healthy people, but those with HIV may be more vulnerable to the drug's detrimental effects.
Muscle spasticity is common in people with ]]>multiple sclerosis]]> (MS) and spinal cord injuries. Marijuana and THC have been tested for their effectiveness in relieving spasticity in small but rigorous clinical studies. One double-blind study examined the effects of marijuana on both people with and without MS. After smoking marijuana, people with MS often thought that their spasticity had improved, however, their posture and balance were actually impaired. This was also true of the participants who did not have MS, although they were not as negatively affected as the participants with MS.
To date, there is sparse clinical evidence on the usefulness of marijuana in treating muscle spasticity. Due to the negative effects of long-term use, smoking marijuana should be discouraged as a means of treating chronic conditions such as MS or spinal cord injury. However, if THC or a related compound does prove to be effective in relieving spasticity, the drug might be beneficial if taken orally.
A small number of clinical trials have examined the effects of marijuana or cannabinoids on neurologic disorders other than MS. These studies have been too small to be conclusive and their results less than promising. Nonetheless, scientists continue to look at the potential for cannabinoids in future treatments for people with ]]>Parkinson’s disease]]> , ]]>Tourette syndrome]]> , ]]>Huntington’s disease]]> , ]]>epilepsy]]> , and ]]>Alzheimer’s disease]]> .
]]>Glaucoma]]> is the second leading cause of blindness in the world. Studies from as early as the 1970s show that marijuana and THC reduce intraocular pressure, a key contributing factor in glaucoma. Although smoked marijuana reduces intraocular pressure, the beneficial effect is of short duration and is accompanied by marijuana intoxication and the respiratory effects of inhaling smoke. In any case, conventional therapies for glaucoma have proven to be more effective than cannabinoids. However, cannabinoids may be worth investigating for the development of new treatments for people who do not respond to available medications.
Undesirable Effects of Smoking Marijuana
According to the National Institute on Drug Abuse, smoking marijuana can cause the following undesirable effects.
- Dry mouth
- Rapid heartbeat
- Loss of coordination and balance
- Slower reaction time, which may pose serious risks for motor vehicle crashes, especially when marijuana and alcohol are used together
- Impaired short-term memory, perception, and judgment
Possible Long-term Effects:
Will the Future of Medicine Go to Pot?
The Institute of Medicine’s researchers “found little reason to recommend crude marijuana as a medicine, particularly when smoked, but they did conclude that active ingredients in marijuana could be developed into a variety of promising pharmaceuticals.” According to the American Medical Association, four main issues comprise the debate on using marijuana as medicine:
- Marijuana is a significant drug of abuse, often leading to abuse among recreational users. Policy-makers have been reluctant to distinguish between the therapeutic uses of marijuana and broader patterns of abuse. Marijuana use is also strongly associated with tobacco use, the most harmful abused substance in most of the world.
- The typical manner of ingesting marijuana involves the burning and inhaling of products from the dried plant, which contains many toxic and cancer-causing chemicals. Thus, it goes completely against the common notion of what is "therapetic" and represents a significant departure from the standard drug approval process.
- Many view smoking marijuana as an alternate, but toxic, delivery system for its active ingredient, THC. However, smoking can allow people more control over their dosage, so that side effects are minimized and therapeutic benefit is achieved. With smoking, the effects of THC are also more rapid, and in some cases, better tolerated, than oral THC. For example, smoking marijuana could provide better drug delivery for people who vomit up their oral medication.
- Some believe that the medical use of marijuana should be determined by risk/benefit analysis in individual patients. For example, use could be determined by seriousness of condition, quality of life impairments, and whether or not a condition is terminal. For acute conditions, it would provide little risk with short-term use.
More evidence is needed to evaluate the medical effectiveness of marijuana’s active ingredients. Further studies are also needed to delineate the benefits and risks of smoking marijuana when used by those with symptoms unresponsive to other drugs including dronabinol.
National Academy of Sciences
Institute of Medicine
Canadian Pharmacists Association
Report 10 of the Council on Scientific Affairs: medical marijuana. American Medical Association website. Available at: http://www.ama-assn.org/ . Accessed on January 24, 2003.
Cannabinoids for pain and nausea [editorial]. BMJ . 2001;323:2-3.
Mack A, Joy JE. Marijuana and Medicine: The Science Beyond the Controversy. National Academy of Sciences; 2000. Available at: http://books.nap.edu/books . Accessed on January 24, 2003
National Institute on Drug Abuse Website. Available at: http://www.drugabuse.gov/ . Accessed on January 24, 2003
Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of motor vehicle crashes after cannabis use. Drug Alcohol Depend. 2004; 73(2):109-119.
*¹9/16/2008 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php : Abrams DI, Jay CA, Shade SB, et al. Cannabis in painful HIV-associated sensory neuropathy: a randomized placebo-controlled trial. Neurology. 2007;68:515-521.
Last reviewed June 2008 by ]]>Jill D. Landis, MD]]>
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