Medical marijuana is legal in 20 states and the District of Columbia, but it is still considered a federal offense to grow, sell, or purchase marijuana.

Because of its therapeutic potential, medicinal marijuana is being prescribed by an increasing number of clinicians for various disorders. However, because of the federal criminalization of marijuana, evidence-based research into its effectiveness has been hindered, and many clinicians still question its scientific legitimacy.1,2

Marijuana, also known as Cannabis sativa, has been used since ancient times for therapeutic, spiritual, and recreational purposes. Clinicians in the United States prescribed marijuana for many different conditions until it was declared illegal and removed from the U.S. Pharmacopeia in 1942.

The Controlled Substance Act of 1970 placed marijuana in the Schedule I category as a substance with high potential for abuse, the same as illicit street drugs.2 Although many anecdotal reports and research studies show its therapeutic value for a number of different disorders, the use of medicinal marijuana has been a controversial topic.

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The two primary compounds that contribute to marijuana’s therapeutic value are tetrahydrocannabinol (THC) and cannabidiol (CBD). Natural marijuana plants contain 5% to 15% THC, the most active ingredient. The variability in THC-to-CBD ratio in different marijuana plants makes dosage standardization difficult.3

THC, the primary psychoactive component of marijuana, binds to cannabinoid receptors in the brain and produces feelings of euphoria, altered sense of time, analgesia, increased appetite, and impaired memory. CBD is a nonpsychoactive compound that is a serotonin receptor agonist with anti-inflammatory and neuroprotective effects.4


The pharmacokinetics of THC vary depending on the route of administration. Medical marijuana can be administered by inhalation or orally. Inhaled THC causes maximum plasma concentration after 15 to 30 minutes, with a duration of two to three hours. Following oral ingestion, effects begin in 30 to 90 minutes and can last up to 12 hours.

The duration of marijuana’s effects depends on dosage; however, it is unclear how to deliver a specific dose of marijuana by smoking.3 Patients report that the inhalation route is the most effective mode of delivery. 

The FDA has approved two oral forms of synthetic THC: dronabinol (Marinol) and nabilone (Cesamet). Patients report that these agents are slow-acting and less effective than inhaled forms of marijuana. Nabiximol (Sativex), an oral mucosal spray, has been approved for medicinal use in Europe only.2

As a Schedule I drug, the marijuana plant has great potential for abuse and dependence, and use of it is restricted. Nabilone is a Schedule II drug, and dronabinol is a Schedule III drug, which indicate that these medications have less abuse potential, do not usually lead to dependence, and are approved for restricted use.2

Therapeutic Uses

Studies show that the most common conditions for which medical marijuana is being prescribed include HIV/AIDS wasting syndrome, cancer chemotherapy, and pain. The American College of Physicians (ACP) recommends medicinal marijuana for the following therapeutic uses:5

  • As an appetite stimulant in HIV/AIDS wasting syndrome

  • As an antiemetic agent in chemotherapy treatment of cancer

  • As an analgesic for cancer pain

  • As an agent in reducing intraocular pressure in glaucoma (however, there is no increased benefit compared with available established drugs) 

  • As an antispasmodic agent in such neuromuscular disorders as multiple sclerosis and spinal cord injury.

Medical marijuana has been shown to be particularly effective in pain management. Marijuana potentiates analgesic effects when used with narcotics, thereby diminishing the dosage of opioids needed for pain relief.6

This article originally appeared on Clinical Advisor