HorticultureResearch

Medicinal Marijuana: Unveiling the Therapeutic Potential

words: Dr. Hyder A. Khoja, Ph.D., M.Sc., A.Ag.

India is a land steeped in faith and mysticism. Ayurveda, combining the Sanskrit words for life and knowledge, is a system of medicine intertwined inextricably with these traits. That a core of belief combined with empirical experimentation could produce a viable medical regimen still widely practiced after well over 5000 years is astounding to Western physicians.

Since prehistoric times, shamans or medicine men and women of Eurasia and the Americas acquired a tremendous knowledge of medicinal plants. The fact that hundreds of additional species were also used by First Nations Canadians suggests that many of these also have important pharmacological constituents that could be valuable in modern medicine.

The use of medicinal plants is not just a custom of the distant past. Perhaps 90% of the world’s population still relies completely on raw herbs and unrefined extracts as medicines. A 1997 survey showed that 23% of Canadians have used herbal medicines. In addition, as much as 25% of modern pharmaceutical drugs contain plant ingredients4.

Among those medicines, one of the most widely used of all psychoactive and medically potent drugs comes from cannabis, one of the first crops to be cultivated by mankind. Despite the fact that its possession and use is illegal in most countries, cannabis is used regularly by as many as 25 million people in North America and Europe and by millions more in other parts of the world1. There has been renewed interest in the potential medical uses of cannabis (Cannabis sativa) in recent years; cannabis was similarly bound to faith and mysticism in India in the past, in the Hindu and Islamic traditions, as well as in numerous other minority religions.

Originating from Central Asia, cannabis is one of the oldest psychotropic drugs known to humanity. The beginnings of its use are difficult to trace, because it was cultivated and consumed long before the appearance of writing. According to archeological discoveries, it has been known in China at least since the Neolithic period, around 4000 BC. There are several species of cannabis. The most relevant are Cannabis sativa, Cannabis indica and Cannabis ruderalis. Among these three; Cannabis sativa, the largest variety, grows in both tropical and temperate climates. The two main preparations derived from cannabis are “cannabis” and “hashish”.

Marijuana is a Mexican term initially attributed to cheap tobacco but referring today to the dried leaves and flowers of the hemp plant. Hashish, the Arabic name for Indian hemp, is the viscous resin of the plant. The Emperor of China, Shen Nung, also the discoverer of tea and ephedrine, is considered to be the first to have described the properties and therapeutic uses of cannabis in his compendium of Chinese medicinal herbs written in 2737 BC. Soon afterwards, the plant was cultivated for its fibre, seeds, recreational consumption and use in medicine. It then spread to India from China. In 1839, William O’Shaughnessy, a British physician and surgeon working in India, discovered the analgesic, appetite stimulant, antiemetic, muscle relaxant and anticonvulsant properties of cannabis. The publication of his observations quickly led to the expansion of the medical use of cannabis. It was even prescribed to Queen Victoria for relief of dysmenorrhea. In 1854, cannabis is also listed in the United States Dispensaries. It was even available in the British Pharmacopoeia in an extract and tincture form for over 100 years. However, after prohibition of alcohol was lifted, the American authorities condemned the use of cannabis, making it responsible for insanity, moral and intellectual deterioration, violence and various crimes. Thus, in 1937, under pressure from the Federal Bureau of Narcotics and against the advice of the American Medical Association, the U.S. Government introduced the Marihuana Tax Act: a tax of $1 per ounce was collected when cannabis was used for medical purposes and $100 per ounce when it was used for unapproved purposes. In 1942, cannabis was removed from the United States Pharmacopoeia, thus losing its therapeutic legitimacy. Great Britain and most European countries banned cannabis by adopting the 1971 Convention on Psychotropic Substances instituted by the United Nations. In the 1990s, officials in the British government noticed something interesting in the nation’s courts: multiple sclerosis (MS) patients charged with marijuana possession were claiming that the plant offered relief from muscle spasms and pain. In 1998, after investigating the issue, the House of Lords Science and Technology Committee issued a report acknowledging the plant’s potential as a source of new drugs and calling for rigorous research “as a matter of urgency2.

 

Un-veiling the therapeutic potential

The therapeutic qualities of medicinal crops are due to the chemical properties they contain. Plants synthesize many compounds called primary metabolites that are critical to their existence8. These include proteins, fats, and carbohydrates that serve a variety of purposes indispensable for sustenance and reproduction, not only for the plants themselves, but also for animals that feed on them.

Plants also synthesize a dazzling array of additional components, called secondary metabolites, whose function has been debated. Many secondary metabolites are antibiotic in a broad sense, protecting the plants against fungi, bacteria, animals, and even other plants.

Every plant species contains chemicals that can negatively affect some animals and microorganisms that consume them, strongly supporting the interpretation that secondary metabolites play a vital role in combating diseases and herbivores. “Plants have been a rich source of medicines because they produce a host of bioactive molecules, most of which probably evolved as chemical defenses against predation or infection.”5

Hence, scientific research and development on cannabis crop and advancement in understanding the cannabinoids over the past 16 years have given rise to a wealth of new opportunities for the development of medically useful cannabinoid-based drugs.

Marijuana is not a completely benign substance. It has proven medicinal potency with a variety of effects. However, the harmful effects to individuals from the perspective of possible medical use of marijuana are not necessarily the same as the harmful physical effects of drug abuse.

Cannabis is a unique source of more than 70 structurally related, plant derived cannabinoids. Although one cannabinoid, THC, is known to cause psychoactive effects associated with the use of illicit herbal cannabis, none of the other cannabinoids is known to cause intoxication. In recent decades, there have been major scientific advances that have led to the discovery of new plant-derived cannabinoids and a cannabinoid receptor system in the human body, or endocannabinoid system. A growing number of states (20 as of March 2014) have legalized marijuana’s use for certain medical conditions in the U.S.

The term “medical marijuana” is generally used to refer to the whole unprocessed marijuana plant or its crude extracts, which are not recognized or approved as medicine by the U.S. Food and Drug Administration (FDA). But scientific study of the active chemicals in marijuana, called cannabinoids, has led to the development of two FDA-approved medications already, and is leading to the development of new pharmaceuticals that harness the therapeutic benefits of cannabinoids while minimizing or eliminating the harmful side effects.

 

 How might cannabinoids be medically useful?

Besides THC, the marijuana plant contains over 200 other cannabinoids. Scientists and manufacturers of designer drugs have also synthesized numerous cannabinoids in the laboratory, some of which are extremely potent.

Currently the two main cannabinoids of interest therapeutically are THC (Tetrahydrocannabinoid) and CBD (cannabidiol), found in varying ratios in the marijuana plant. THC stimulates appetite and reduces nausea (and there are already approved THC-based medications for these purposes), but it may also decrease pain, inflammation, and spasticity. CBD is a non-psychoactive cannabinoid that may also be useful in reducing pain and inflammation, controlling epileptic seizures, and possibly even treating psychosis and addictions.

Research funded by the NIH (National Institute of Health-USA) is actively investigating the possible therapeutic uses of THC, CBD, and other cannabinoids to treat autoimmune diseases, cancer, inflammation, pain, seizures, substance use disorders, and other psychiatric disorders.

 

What current medications contain cannabinoids?

An FDA-approved drug called Dronabinol (Marinol®) contains THC and is used to treat nausea caused by chemotherapy and wasting disease (extreme weight loss) caused by AIDS. Another FDA-approved drug called Nabilone (Cesamet®) contains a synthetic cannabinoid similar to THC and is used for the same purposes.

A drug called Sativex®, which contains approximately equal parts THC and CBD, is currently approved in the UK and several European countries to treat spasticity caused by multiple sclerosis (MS). It is established as an effective and safe cancer pain treatment. And a CBD-based drug called Epidiolex has recently been created to treat certain forms of childhood epilepsy. Some parents of children with a severe form of epilepsy called “Dravet Syndrome” have reported success in using a high-CBD strain of marijuana to control seizures in their children.

There are major questions regarding just how beneficial medicinal herbs can be, and just how harmful they can be. As pointed out above, plants contain a very wide variety of secondary compounds. It is clear that some of these compounds, at least in a pure state and at some dosage, are medicinal or toxic. However, it does not necessarily follow that the same compounds present in the herb are as toxic or medicinal as when extracted from the herb, since synergistic (interactive) effects of the chemical components of the herb are possible.

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