Cannabinoids are active chemicals in cannabis that cause drug-like effects throughout the body, including the central nervous system and the immune system. They are also known as phytocannabinoids. The main active cannabinoid in cannabis is delta-9-THC. Another active cannabinoid is cannabidiol (CBD), which may relieve pain and lower inflammation without causing the “high” of delta-9-THC.
Cannabinoids may be useful in treating the side effects of cancer and cancer treatment.
Other possible effects of cannabinoids include:
- Anti-inflammatory activity.
- Blocking cell growth.
- Preventing the growth of blood vessels that supply tumors.
- Antiviral activity.
- Relieving muscle spasms caused by multiple sclerosis.
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The History of medical use of cannabis
The use of cannabis for medicinal purposes dates back at least 3,000 years. It came into use in Western medicine in the 19th century and was said to relieve pain, inflammation, spasms, and convulsions.
In 1937, the U.S. Treasury began taxing cannabis under the Marijuana Tax Act at one dollar per ounce for medicinal use and one hundred dollars per ounce for non-medical use. The American Medical Association (AMA) opposed this regulation of cannabis and did not want studies of its potential medicinal benefits to be limited. In 1942, cannabis was removed from the U.S. Pharmacopoeia because of continuing concerns about its safety. In 1951, Congress passed the Boggs Act, which included cannabis with narcotic drugs for the first time. Under the Controlled Substances Act passed by Congress in 1970, marijuana was classified as a Schedule I drug.
Although cannabis was not believed to have any medicinal use, the U.S. government distributed it to patients on a case-by-case basis under the Compassionate Use Investigational New Drug (IND) program started in 1978. This program was closed to new patients in 1992.
Researchers have studied how cannabinoids act on the brain and other parts of the body. Cannabinoid receptors (molecules that bind cannabinoids) have been discovered in brain cells and nerve cells in other parts of the body. The presence of cannabinoid receptors on immune system cells suggests that cannabinoids may have a role in immunity.
Nabiximols (Sativex) is a Cannabis extract that contains delta-9-THC and cannabidiol (CBD). Nabiximols is approved in Canada (under the Notice of Compliance with Conditions) for relief of pain in patients with advanced cancer or multiple sclerosis.
Preclinical studies of cannabinoids have investigated the following:
- Studies in mice and rats have shown that cannabinoids may inhibit tumor growth by causing cell death, blocking cell growth, and blocking the development of blood vessels needed by tumors to grow. Laboratory and animal studies have shown that cannabinoids may be able to kill cancer cells while protecting normal cells.
- A study in mice showed that cannabinoids may protect against inflammation of the colon and may have potential in reducing the risk of colon cancer, and possibly in its treatment.
- A laboratory study of delta-9-THC in hepatocellular carcinoma (liver cancer) cells showed that it damaged or killed the cancer cells. The same study of delta-9-THC in mouse models of liver cancer showed that it had anti-tumor effects. Delta-9-THC has been shown to cause these effects by acting on molecules that may also be found in non-small cell lung cancer cells and breast cancer cells.
- A laboratory study of cannabidiol (CBD) in estrogen receptor positive and estrogen receptor negative breast cancer cells showed that it caused cancer cell death while having little effect on normal breast cells. Studies in mouse models of metastatic breast cancer showed that cannabinoids may lessen the growth, number, and spread of tumors.
- A review of 34 studies of cannabinoids in glioma tumor models found that all but one study showed that cannabinoids can kill cancer cells without harming normal cells.
- A laboratory study of cannabidiol (CBD) in human glioma cells showed that when given along with chemotherapy, CBD may make chemotherapy more effective and increase cancer cell death without harming normal cells. Studies in mouse models of cancer showed that CBD together with delta-9-THC may make chemotherapy such as temozolomide more effective.
- Many animal studies have shown that delta-9-THC and other cannabinoids stimulate appetite and can increase food intake.
- Cannabinoid receptors (molecules that bind cannabinoids) have been studied in the brain, spinal cord, and nerve endings throughout the body of animals to understand their roles in pain relief.
- Cannabinoids have been studied for anti-inflammatory effects that may play a role in pain relief.
- Animal studies have shown that cannabinoids may prevent nerve problems (pain, numbness, tingling, swelling, and muscle weakness) caused by some types of chemotherapy.
Nausea and vomiting
- Cannabinoid receptors found in brain cells may have a role in controlling nausea and vomiting. Animal studies have shown that delta-9-THC and other cannabinoids may act on cannabinoid receptors to prevent vomiting caused by certain types of chemotherapy.
Anxiety and sleep
- Cannabinoid receptors found in the brain and other parts of the nervous system may be involved in controlling mood and anxiety.
- Anti-anxiety effects of cannabidiol (CBD) have been shown in several animal models.