Weighing the Benefits and Risks of Medical Marijuana

A Conversation With David J. Casarett, MD, MA

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Guest Editor

Jamie H. Von Roenn, MD

Jamie H. Von Roenn, MD

Addressing the evolving needs of cancer survivors at various stages of their illness and care, Palliative Care in Oncology is guest edited by Jamie H. Von Roenn, MD. Dr. Von Roenn is ASCO’s Senior Director of Education, Science and Professional Development Department.

Despite the fact that 28 states and the District of Columbia have enacted laws to permit the use of cannabis and cannabinoid-based drugs to treat medical conditions, including cancer and symptoms from its treatment, federal law prohibits physicians from prescribing marijuana to their patients, creating a delicate legal—and ethical—dilemma for physicians.

The U.S. Drug Enforcement Administration classifies marijuana, either for medical or recreational use, as a Schedule 1 drug under the Controlled Substances Act of 1970, the same class as heroin and LSD, prohibiting it from being distributed, dispensed, or possessed. And although the U.S. Department of Justice updated its marijuana enforcement policy in 2013 in recognition of state laws legalizing medical marijuana and advising state attorneys not to pursue legal action against physicians in those states, it reserved the right to take legal action against individuals, including physicians, who may be violating federal law.1

Even in states legalizing the sale and use of medical marijuana, physicians can only write letters of recommendation—not prescriptions—stating that a patient qualifies for a certification to use the substance. In addition, physicians are not allowed to dispense the drug; patients must go to a licensed dispensary to obtain it.

Mixed Picture of Health Benefits

Although the two main compounds found in cannabis, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have been widely used for treating disease and alleviating symptoms, a meta-analysis of 79 randomized trials that compared cannabinoids with usual care, placebo, or no treatment for nausea and vomiting due to chemotherapy; appetite stimulation in HIV/AIDS; chronic pain; spasticity due to multiple sclerosis or paraplegia; depression; anxiety; insomnia; psychosis; glaucoma; or Tourette syndrome, has found mixed results on their effectiveness.2 According to the study results, there was moderate-quality evidence suggesting the use of cannabinoids for the treatment of chronic pain and spasticity and only low-quality evidence on their effectiveness for improving nausea and vomiting due to chemotherapy, weight gain in HIV infection, sleep disorders, and Tourette syndrome.

If I were allowed to legally prescribe marijuana, I would counsel my patients about its risks and benefits the same way I counsel them about any other drug I prescribe; then we would make a decision together on whether it is the best choice.
— David J. Casarett, MD, MA

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Currently, only two drugs based on marijuana compounds have been approved by the U.S. Food and Drug Administration (FDA) for medical use: dronabinol and nabilone (Cesamet). Nabiximols (Sativex), a mucosal spray containing THC and CBD, for the treatment of chronic pain from cancer and muscle spasms and pain from multiple sclerosis is under review by the FDA, although it has been approved in Canada and numerous countries in the European Union for neuropathic pain control.

In July 2016, ASCO released a new clinical practice guideline on the management of chronic pain in adult cancer survivors.3 The guideline calls for the use of a variety of evidence-based strategies for treating pain, including routine screening for chronic pain; use of alternative pain management approaches, such as hypnosis and meditation; medical cannabis in states where it is legalized; and assessment of patients for the potential for opioid overuse.

At the 2016 Palliative Care in Oncology Symposium in San Francisco, David J. Casarett, MD, MA, Chief of Palliative Care and Professor of Medicine at Duke University Health System, gave a presentation on the potential benefits and risks of medical marijuana in the care of patients with advanced cancer and the dichotomy between the enthusiasm for its use and the evidence supporting it.

The ASCO Post talked with Dr. ­Casarett, author of Stoned: A Doctor’s Case for Medical Marijuana (Penguin Random House, 2015), about the risks and benefits of using legal cannabis in the palliative care setting for the symptoms and treatment of cancer and how the various delivery systems, including smoking, vaping, and ingesting through food or sublingual sprays, are absorbed in the body.

Benefits and Risks

What are the benefits and risks of using medical marijuana in the palliative care setting?

The indications for cannabinoids for which the data are clearest include treatment for neuropathic pain, loss of appetite, and muscle spasms, especially in the setting of multiple sclerosis. That doesn’t mean cannabinoids don’t work for other symptoms, but these are the indications that have the greatest evidence for effectiveness so far.

In terms of the risks, there are many proposed or claimed risks in the use of marijuana, some of which have been discussed and proven to be true or debunked or are still being investigated. Some of the risks we know to be true include impaired driving ability and drowsiness, which is on the same level as alcohol and other recreational drugs. Other risks include addiction, psychotic episodes, and cannabionoid hyperemesis syndrome, which consist of nausea and vomiting that resolves when marijuana use is discontinued. Some people have problems with increased heart rate, decreased blood pressure, dizziness or lightheadedness, and fainting.

Cannabis is thought to be effective for symptoms such as anxiety, insomnia, and posttraumatic stress disorder; although there are no randomized control data to support that assertion, many patients I talk to say it does help with these symptoms.

When to Consider Medical Marijuana

If medical marijuana were legal in your state (North Carolina), would you prescribe it for your patients suffering from treatment symptoms?

Yes, definitely, because we know it is beneficial in certain circumstances. However, whether it’s appropriate for an oncologist to recommend marijuana to patients probably depends on a couple of questions. One is, as we’ve discussed, are there good data showing effectiveness for a patient’s specific symptoms. And, two, what other treatments have been tried? For instance, I probably wouldn’t recommend marijuana as a first-line treatment for chemotherapy-induced nausea. But if the patient is having recurrent bouts of nausea that are refractory to drugs such as ondansetron, haloperidol, or prochlorperazine, it might be reasonable to consider a trial of marijuana.

If I were allowed to legally prescribe marijuana, I would counsel my patients about its risks and benefits the same way I counsel them about any other drug I prescribe; then we would make a decision together on whether it is the best choice. All drugs have risks and benefits, so from my standpoint, I don’t see medical marijuana being that different from other drugs. It’s just a matter of making sure that patients have realistic expectations about its benefits and that they are counseled about its risks, so they are informed and can minimize those risks.

Would you monitor those patients for side effects or problems the way you would for any other drug you prescribed?

Yes. Many people who use medical marijuana use it without the knowledge of a health-care provider, and without monitoring, and that is potentially a problem. In an ideal world, any physician who recommends medical marijuana as a treatment should be in a position to monitor the patient for side effects, including the risk of addiction.

Cancer Cachexia

Is there scientific evidence that marijuana may be beneficial for symptoms such as cachexia?

Yes and no. There are data suggesting that marijuana increases appetite, so for some patients who have a loss of appetite and want to participate in family meals, marijuana could be helpful. But if the goal is to gain weight, especially lean muscle mass, there is no evidence showing marijuana is beneficial. Cancer cachexia is a tough problem to solve.

That said, the possibility of just being able to increase a patient’s appetite may be reason enough to recommend marijuana. I’ve had patients tell me that marijuana allowed them to feel hungry enough to sit at a table with family members for a meal. They didn’t care if it helped them gain weight. Just being able to participate in such a routine ritual with their family was enough.

Delivery Methods

There are many delivery methods of cannabis, including smoking, ingesting it through food, or inhaling it. Is one method more effective than another?

Smoking and vaporizing marijuana basically offer the same way of getting active cannabinoids, such as CBD and THC, into the bloodstream and to the brain quickly. This method is also easier to titrate than other delivery methods, so a patient can adjust the number of puffs he or she takes until the needed level of relief is reached.

The other most common delivery mechanism is in edible form. However, THC and CBD in food are metabolized in the liver, and the gastrointestinal route has a delayed absorption compared with inhalation. That means there is a delayed response, which can make it difficult for people to determine how much to eat to receive an appropriate dose to achieve the desired effect. In addition, about half of the cannabinoids taken by mouth become inactivated, so the overall effect is not as great as it is with smoking the same dose.

Then there are tinctures, which are cannabinoids that are dissolved in small amounts of alcohol and swallowed. The mucosal spray nabiximols is a tincture that is being reviewed by the FDA for approval.

More Openness Among Oncologists

Is medical marijuana becoming a more acceptable component of cancer care?

It is difficult to say. The oncologists I’ve talked with about its use are more comfortable discussing marijuana with patients now than they used to be. However, many don’t want to be in the position of writing either a prescription or a letter of recommendation for it. 

For what it is worth, my sense is that there is more openness among oncologists than among general practitioners about its value in the patient care setting, because they are the ones taking care of patients with advanced cancer. But we need more evidence-based data to determine marijuana’s benefit in the palliative care setting before we can say with certainty under which circumstances to recommend it to patients. We also need legal clarity to avoid any potential professional risk.

For more information on medical marijuana, see the November 10, 2016, issue of The ASCO Post. ■

Disclosure: Dr. Casarett reported no potential conflicts of interest.


1. U.S. Department of Justice: Justice Department Announces Update to Marijuana Enforcement Policy, August 29, 2013. Available at Accessed December 13, 2016.

2. Whiting PF, Wolff RF, Deshpande S, et al: Cannabinoids for medical use: A systematic review and meta-analysis. JAMA 313:2456-2473, 2015.

3. Paice JA, Portenoy R, Lacchetti C, et al: Management of chronic pain in survivors of adult cancers: American Society of Clinical Oncology Clinical Practice Guideline. J Clin Oncol 34:3325-3345, 2016.