Medical Cannabis: Therapeutic Potential and Controversies

Medical cannabis, a herbal remedy derived from Cannabis genus plants, is utilized in the treatment of specific symptoms or diseases. The term cannabis, which specifically refers to the plant genus, is often used interchangeably with marijuana, which describes the raw drug extracted from the plants’ leaves and flowers.

Cannabis has a long-standing history as an analgesic (pain reliever) and antispasmodic agent in medical use. However, its medical benefits remained largely unrecognized by scientists and physicians for much of the modern era. The discovery of the active ingredient tetrahydrocannabinol (THC) in the 1960s, and the subsequent identification of a system of endogenous cannabinoid receptors and ligands in the late 1980s and early 1990s, sparked interest in the therapeutic potential of cannabis, its extracts, and derivatives. This research revealed that cannabis could provide relief for conditions such as severe chronic pain, leading to the development of various herbal medical cannabis products.

Herbal Cannabis in Medicine

Several pharmaceutical drugs derived from cannabis, in purified and standardized form, are available for medical use. However, the use of herbal cannabis in medicine remains a contentious issue, largely due to the lack of standardization among products to ensure safe and consistent dosing, and disagreements over legalization. For instance, in the United States, while cannabis cultivation, possession, and consumption are illegal, some states have legalized the use of herbal medical cannabis specifically. The U.S. Food and Drug Administration has approved products such as cannabidiol (CBD), an active ingredient in cannabis, and synthetic cannabis-like drugs like dronabinol and nabilone. While some European countries permit the use of herbal medical cannabis, it remains illegal in the United Kingdom, which does allow the prescription of a cannabis-based drug called nabiximols (Sativex).

Use of Medical Cannabis

Beyond Canada and the Netherlands, there is no inherent distinction between herbal cannabis used recreationally and that used medically. Therefore, medical cannabis can be best described as the use of cannabis under continuous medical supervision, with a confirmed diagnosis of the target symptom-disease complex. Herbal cannabis is used along with, or in consideration of, other pharmacological and nonpharmacological approaches, aiming to achieve pre-determined treatment outcomes. Anecdotal reports and randomized clinical trial results suggest that cannabis may be beneficial in managing various conditions, including pain, spasticity, nausea, anorexia, and seizures.

Unsupervised use of cannabis is not considered medical cannabis. The same applies to cannabis prescribed by a physician who has not adequately evaluated the patient, does not include cannabis in a broader care model, or does not monitor the patient for subjective and objective outcomes or adverse events. Studies in the first decade of the 21st century estimated that self-reported cannabis use among those with various conditions ranged from 30 to 50 percent (HIV/AIDS) to 10 percent (multiple sclerosis and epilepsy).

Effectiveness of Medical Cannabis

Medical cannabis is most commonly administered by smoking or vaporization, or in the form of edible preparations. None of these methods have been standardized, and the effectiveness of edible cannabis preparations has not been evaluated in clinical trials. Smoked cannabis has been evaluated in a few randomized controlled trials involving patients suffering from neuropathic pain conditions. In each of these trials, patients experienced a reduction in pain intensity at THC concentrations of 3.9 percent or higher. The adverse events from these studies were mild to moderate and included drowsiness, dizziness, and dry mouth. No serious or severe adverse events were reported.

Medical Precautions

A significant safety concern associated with medical cannabis is the potential for medical use to encourage or transition into recreational use, which is associated with side effects ranging from acute to chronic. Acute effects include intoxication, impaired cognition and motor function, elevated heart rate, anxiety, and psychosis in predisposed individuals. Chronic effects include bronchitis (from smoked cannabis), psychological cannabis dependency, loss of motivation, and cognitive deficits. These effects seem to disappear upon abstinence.

Medical cannabis may be riskier and potentially contraindicated for patients with a personal or family history of psychosis, unstable cardiac disease, and lung disease. Medical cannabis users are advised by physicians not to use tobacco, either alone or mixed with cannabis. They are also advised not to drive or operate machinery while initiating or changing doses and if impaired by the drug. Apart from possible synergistic effects of cannabis with other psychotropic medications, such as sedatives and hypnotics, no major drug-drug interactions are known.

The primary goal of medical cannabis use is symptom relief, improved function, and overall quality of life. Reductions in doses (if not complete cessation) of other medications should be strongly considered. However, clinical evidence of such outcomes is lacking, and it remains the responsibility of the treating physician and the patient to work toward the achievement of mutually agreed-upon goals.