Scientists are testing lots of different medical uses for marijuana

by Dr. Mark Thoma, MD
There are two preparations of marijuana that are available for use in the US currently.
Dronabinol (Marinol®, delta9-THC) can be prescribed for chemotherapy-induced nausea and vomiting (CINV) and anorexia with weight loss in patients with AIDS. Nabilone can be used to treat CINV, as well. Dronabinol is an isomer of THC, the chemical in marijuana that gets you high, while nabilone is a synthetic form of THC. Both medications are for oral use, and this can limit their effectiveness when used to combat nausea and vomiting. A patient vomiting frequently may not be able to retain a dose of either medication.

The effectiveness of the drugs to prevent or modify CINV seems to be related to exactly which chemotherapy agents are being given to the patient in question.

There are two other medications undergoing trials prior to FDA approval. The first is is an oral medication containing cannabidiol, which is being investigated to be used for the treatment of two rare forms of epilepsy and as a possible treatment for schizophrenia. The other THC-based medication undergoing trials, nabiximols, is a pain-relieving marijuana extract prepared in the form of an oral spray.

Therefore, it can be absorbed through the mucous membranes of the mouth and does not need to be swallowed. These trials are of particular interest because they are using marijuana-based medications for purposes other than suppressing vomiting or promoting weight gain, which have been the previous reasons for using them.
Studies of dronabinol have shown it’s effectiveness in reducing CINV, either when used alone or when given with other anti-emetics.

It has also been used to treat radiation-induced nausea and vomiting, and is also useful for causing some weight gain in a number of patients with AIDS who have been treated with it.
Nabilone is also effective in treating CINV. Additionally, it has been used, in a limited fashion, to treat things like neuropathic pain, Parkinson’s disease, multiple sclerosis, spasticity, inflammatory bowel disease and some others symptoms and conditions.

Marijuana for pain management
In many of the above studies, the investigators could measure some physical sign to determine if the drug was working. They could measure increase in calories consumed, weight gain, fewer episodes of vomiting or some other parameter. However, it’s a bit harder to measure if a drug is effective in relieving pain. In some studies, the researchers asked the patients if their pain had decreased. This always adds a large measure of subjective bias. The patient may want to please the investigator and will say “yes” even if the pain hasn’t decreased.

Or the pain may be less, or perceived as less, on a specific day for some other reason. Perhaps the pain has decreased because treatment with other drugs is succeeding. The patient may be happier because of a family visit or planned discharge from the hospital and report less pain as a result. There are some physical methods for measuring pain. For example, healthy volunteers may be used, subjected to mild, controlled pain and their limits ascertained before and after a dose of the medication being tested. There are other methods, as well. But there is always an inherent problem with measuring responses like these that may not be such of a factor in studies where purely physical factors can be weighed.

Also, when measuring pain, there can be an increase in pain tolerance as well as a decrease in pain sensitivity. With an increase in pain tolerance, the patient can take more pain before reporting that they are in pain. Some studies looked at pain tolerance. Some looked at pain sensitivity. Some at both. Some just asked the patient’s judgement as to how much pain they were in. So it may be difficult to compare one study with another because of this, and other factors. Additionally, the drug used may have differed in one study vs. another (nabilone vs. smoked marijuana), the concentration of THC in the smoked marijuana was different, the amount of marijuana smoked would vary in different trials, etc.

And some of the studies used pain generated by the experimenters, while other studies used pain that the patients had from intrinsic sources.
Keeping the above in mind, there have been a number of studies run on using marijuana and cannabinoids to control pain. In a few studies, marijuana (or a medicinal version thereof) reduced pain when used on its own. Some of these were done on patients experiencing neuropathic pain, often a burning type of pain that many diabetics and some AIDS patients experience.

Nabiximols seemed to be able to control cancer pain in a number of small trials, while THC didn’t give any significant relief in cancer patients. One small study showed that marijuana plus opiates produced better pain control for patients than opiates alone.
At least two studies showed that the THC concentration of smoked marijuana was relatively unimportant — that is, high THC concentration produced no more pain relief than lower THC concentration. Interestingly, one study demonstrated that smoked marijuana with a high THC concentration actually increased patient’s perception of pain. Another study showed that the longer marijuana was used during the study, the more effective it was for controlling pain.

Marijuana via Shutterstock

Because of the caveats that I mentioned earlier, it’s not possible to make sweeping statements about the effectiveness of marijuana (or THC or other marijuana-derived medications) for pain control. They do seem to have been effective in the studies that I mentioned, for the specific types of pain that were assessed in the trials. A number of patients/volunteers in the studies reported a significant decrease in pain when treated with these drugs. Some cancer patients got pain relief when treated with some marijuana derivatives while other marijuana derivatives didn’t provide significant relief. Some cancer patients got better relief when cannabinoids were added to their opiate regime.

So, can this class of medication relieve pain? The answer is a qualified “yes.” A degree of pain relief can be achieved in some instances in a reasonable number of patients. That degree depends upon large number of factors: exact drug used, dose, frequency of dose, type of pain the patient is experiencing, concentration of THC in smoked materials and others. More research will need to be done before more concrete information is available.

Marijuana as an anti-tumor drug
Some solid tumor cells have been shown to have receptors that will allow cannabinoids and cannabinoid-like substances to bind there. When a compound binds to a receptor, it most often triggers some response by the cell. The bound material may get transported into the cell. The saturated receptor may trigger the cell’s internal organelles to produce something, or other actions could occur. Researchers have run trials using marijuana-class drugs on tumors with these receptors both in vitro and in vivo.

These are early studies and others are to follow. Cancer types that have been treated with marijuana-derivative drugs include: lung, gloom (a form of brain cancer), prostate, hepatocellular cancer and some others.
In one study that tested using a marijuana-based drug to treat rats with lung cancer, the scientists showed that the lung cancer had a decreased rate of metastasis (it spread more slowly) when the rats were treated. Research on gliomas showed that it is safe to inject marijuana-derivative drugs directly into the growing brain tumor safely. As one academic review of work done using cannabinoids on gliomas said:

The anti tumor activity [of cannabinoids] included: antiproliferative effects (cell cycle arrest), decreased viability and cell death by toxicity, apoptosis, necrosis, autophagy, as well as antiangiogenic and antimigratory effects. Antitumoral evidence included: reduction in tumor size, antiangiogenic, and antimetastatic effects. Additionally, most of the studies described that the canabinnoids exercised selective antitumoral action in several distinct tumor models.

Thereby, normal cells used as controls were not affected. The safety factor in the cannabinoids’ administration has also been demonstrated in vivo. The various cannabinoids tested in multiple tumor models showed antitumoral effects both in vitro and in vivo. These findings indicate that cannabinoids are promising compounds for the treatment of gliomas.

Other research has shown that cannabinoids have also has similar effects in some other tumor types like prostate carcinoma, some types of breast carcinoma and cancers.
It’s important to note that much of this research is in very early stages. Most has been done in cell culture and/or in animal models. Only a few studies have been done in humans. But there are more studies in progress.
Marijuana-derived drugs may be useful to treat some types of cancer, in conjunction with other standard chemotherapy regimens, radiation and surgery, but they are not available (nor indicated) for that use today.
As mentioned above, some research on use of cannabinoids for a variety of other diseases is also in progress.

These studies include ones looking at any benefits from cannabinoids on: multiple sclerosis, Parkinson’s disease, some rare forms of epilepsy, some post-stroke syndromes, inflammatory bowel disease, schizophrenia and others. As with most of the above, this research is still in its early stages and not ready for commercial use yet.

Adverse reactions with cannabinoids and marijuana
There are some potential problems with using marijuana and its fractions that may need to be considered.
Marijuana can act as an intoxicant and cause impaired driving and may increase auto accidents. In combination with alcohol, these results can be magnified.
Some researchers have found that marijuana can have negative effects on memory, motor skills, time needed to react to a novel situation, maintaining attention on a task and other skills.

Marijuana smoke produces carcinogens, as does cigarette smoking. There is thought to be a risk of developing cancer (lung, oral, throat, etc.) from marijuana smoke. But the evidence from a few studies is mixed. So whether smoked marijuana is a significant to produce cancer is unknown. It also seems, from limited data, that marijuana smoking does not cause chronic obstructive pulmonary disease (COPD), as cigarette smoking does.

So, while there are some possible contraindications for using marijuana and/or cannabinoids, they may be minimal when compared to some of the possible benefits. Those already known: anti-nausea, anti-emetic, anti-weight loss effects; and those that are possible: pain control, antineoplastic and possibly additional uses in neurologic and other diseases.