National Cancer Institute - Cannabis and Cannabinoids (PDQ®)

From the National Cancer Institute

History

Cannabis use for medicinal purposes dates back at least 3,000 years. It was introduced into Western medicine in the 1840s by W.B. O’Shaughnessy, a surgeon who learned of its medicinal properties while working in India for the British East Indies Company. Its use was promoted for reported analgesic, sedative, anti-inflammatory, antispasmodic, and anticonvulsant effects.

In 1937, the U.S. Treasury Department introduced the Marihuana Tax Act. This Act imposed a levy of one dollar an ounce for medicinal use of Cannabis and one hundred dollars an ounce for recreational use. Physicians in the United States were the principal opponents of the Act. The American Medical Association (AMA) opposed the Act because physicians were required to pay a special tax for prescribing Cannabis, use special order forms to procure it, and keep special records concerning its professional use. In addition, the AMA believed that objective evidence that Cannabis was addictive was lacking and that passage of the Act would impede further research into its medicinal worth.[6] In 1942, Cannabis was removed from the U.S. Pharmacopoeia because of persistent concerns about its potential to cause harm.

In 1951, Congress passed the Boggs Act, which for the first time, included Cannabis with narcotic drugs. In 1970, with the passage of the Controlled Substances Act, marijuana was classified as a Schedule I drug. Drugs in this category are distinguished as having no accepted medicinal use. Other Schedule I substances include heroin, LSD, mescaline, methaqualone, and gamma-hydroxybutyrate.

Despite its designation as having no medicinal use, Cannabis was distributed to patients by the U.S. government on a case-by-case basis under the Compassionate Use Investigational New Drug program established in 1978. Distribution of Cannabis through this program was discontinued in 1992. In 2010, the U.S. Department of Veteran Affairs approved marijuana use for patients in states where its medicinal use is legal.

The main psychoactive constituent of Cannabis was identified as delta-9-tetrahydrocannabinol (THC). In 1986, synthetic delta-9-THC in sesame oil was licensed and approved for the treatment of chemotherapy -associated nausea and vomiting under the generic name dronabinol. Clinical trials determined that dronabinol was as effective as or better than other antiemetic agents. Dronabinol was also studied for its ability to stimulate weight gain in patients with AIDS in the late 1980s. Clinical trial results showed no significant weight gain, although patients reported an improvement in appetite.

Within the past 20 years, the neurobiology of cannabinoids has been analyzed. The first cannabinoid receptor, CB1, was pharmacologically identified in the brain in 1988. A second cannabinoid receptor, CB2, was identified in 1993. The highest concentration of CB2 receptors is located on B lymphocytes and natural killer cells, suggesting a possible role in immunity. Endogenous cannabinoids (endocannabinoids) have been identified and appear to have a role in pain modulation, control of movement, feeding behavior, and memory.