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Cannabis Has Potential as a Drug to Relieve the Side Effects of Cancer and Its Treatment

Cannabis Has Potential as a Drug to Relieve the Side Effects of Cancer and Its Treatment

ABSTRACT: "From My Viewpoint" features essays from experts on vital issues in cancer care. This month, Donald I. Abrams, MD, professor of clinical medicine, University of California, San Francisco (UCSF), Comprehensive Cancer Center, and chief of hematology-oncology, San Francisco General Hospital, discusses the contentious issue of medical marijuana from his opinion and perspective as a physician and clinical trial researcher.

Cannabis has been used as a medicine for thousands of years. A body of evidence suggests that this plant, which contains hundreds of active compounds, has potential value for certain patients undergoing cancer treatment. However, largely due to nonscientific political issues, marijuana is still classified as a schedule I drug—an illegal substance having a "high potential for abuse" and "no currently accepted medical use in the United States." This classification, which has been repeatedly challenged, greatly complicates scientific research of this plant's medical potential.

Cannabis was first introduced into Western medicine in the 1840s to counteract pain, spasm, and inflammation. It found a place in the medical literature of the day as a treatment for a number of diverse conditions. In the early 1900s, as other pharmaceutical agents were developed for these indications, interest in marijuana began to fade. The first federal restriction on marijuana was the Marijuana Tax Act of 1937, which imposed cost-prohibitive taxes for the medical or recreational use of the drug.

At that time, the American Medical Association (AMA) opposed the restrictive tax, citing a lack of objective data regarding marijuana's purported harmful effects and fearing that further investigations into its efficacy would be impeded. Ultimately, marijuana was removed from the United States Pharmacopoeia (USP) in 1942.

About every 10 years since 1942, the federal government has commissioned a study group to evaluate the medical potential of cannabis. The most recent of these groups—the 1997 National Institutes of Health Workshop on the Medical Utility of Marijuana and the 1999 Institute of Medicine (IOM) report Marijuana and Medicine: Assessing the Science Base—identified several medical conditions in which marijuana warranted further research: appetite stimulation, nausea and vomiting, analgesia, and neurological and movement disorders. These potential benefits, which could also help relieve side effects of cancer or its treatment, are certainly relevant to the patients we treat.

The IOM report included caveats cautioning that although marijuana has shown some benefits, they are generally weak and other more potent agents are currently available, such as our potent antiemetic agents. The report also expressed concern about a smoked medicine and urged the development of smokeless delivery systems. One such system is already felt to exist in the form of synthetic delta-9-tetrahydrocannabinol (THC) (dronabinol), marketed as Marinol capsules. Marinol was approved by FDA in 1986 for the treatment of chemotherapy-induced nausea and vomiting.

So why should we study marijuana when we have an approved drug? For one, delta-9 THC—the single most psychoactive compound of the herb—has been on the market for 2 decades; therefore, it seems illogical from a scientific perspective not to study the properties of the whole plant if one of its constituent components has proven medicinal value.

In 1992, the indication for dronabinol was expanded to include the treatment of anorexia associated with the wasting syndrome in patients with AIDS. However, many patients taking dronabinol complained about being too heavily sedated for too long. Oral dronabinol has low bioavailability (6% to 20%) and a long half-life. Peak plasma concentrations occur within 1 to 6 hours and may remain elevated for several hours. On the other hand, patients who use smoked marijuana as an appetite stimulant seemed to enjoy more control over the drug's effects.

At that time, there were no effective treatments for HIV, and the associated wasting syndrome was ravaging the patient population. We noticed that our patients with HIV-induced anorexia who smoked marijuana showed an increase in appetite, relief of pain symptoms, and improved mood. Consequently, my colleagues and I decided a study was warranted looking at the efficacy of smoked marijuana as an appetite stimulant to counteract the devastating anorexia and weight loss in HIV-infected patients.

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