Cannabis oil with THC found safe but fails to cut Parkinson’s pain
After small study, researchers call for larger trials using higher concentrations
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- An oral cannabis oil containing CBD and THC was found to be generally safe and well-tolerated in people with Parkinson's in a small trial.
- The treatment failed, however, to significantly reduce chronic pain or ease other nonmotor symptoms compared with a placebo.
- Researchers recommend conducting larger clinical trials with higher concentrations to determine potential therapeutic effectiveness.
A commercially available oral cannabis oil — containing two natural compounds found in the plant, one with psychoactive properties — appeared to be generally safe for people with Parkinson’s disease, but failed to reduce pain or ease other symptoms among participants in a small mid-stage clinical trial.
The tested oil contains both cannabidiol (CBD) and tetrahydrocannabinol (THC), the compound in cannabis that causes a high and has been suggested for use for pain and muscle spasms in people with Parkinson’s. CBD, which is nonintoxicating, has been thought to help ease anxiety and other nonmotor Parkinson’s symptoms.
The Phase 2 study, conducted by researchers in Brazil over a roughly two-month period, found that the cannabis oil did not ease long-lasting pain or other nonmotor Parkinson’s symptoms compared with a placebo, though the team noted that “the cannabis extract was safe and well-tolerated.”
“The use of an oral oil containing CBD and THC for [nine] weeks did not result in a significant improvement in pain compared with [the] placebo,” the researchers wrote.
While this study did not find benefits, the team noted that only a small number of patients were involved. Thus, the researchers called for additional studies enrolling a larger number of participants and using higher concentrations of CBD and THC.
The study, “Cannabis-Based Oil for Pain and Other Non-Motor Symptoms in Parkinson’s Disease: A Randomized Controlled Trial,” was published as a brief report in the journal Movement Disorders.
Parkinson’s is known for its hallmark motor symptoms, notably tremor. But the progressive disease can also cause nonmotor symptoms such as pain, anxiety, depression, and problems with sleeping, breathing, or keeping blood pressure under control. There are limited treatments now available that are specifically aimed at these symptoms.
Study stopped early due to lack of benefit
Cannabis contains cannabinoids, compounds that may help ease symptoms of many diseases, including Parkinson’s. Some patients report benefits for both motor and nonmotor symptoms, and the use of medical cannabis has increased as it becomes legal in a wider range of countries.
To better understand the potential benefits of cannabis for nonmotor symptoms, the researchers tested a commercially available oil made from Cannabis sativa L. The oil contained two cannabinoids: 96 mg of CBD and 2.1 mg of THC per milliliter. Unlike CBD, THC is a psychoactive compound that can alter perception.
The study enrolled 101 adults with Parkinson’s who had chronic pain, meaning pain that had lasted or returned for at least three months. The participants were randomly assigned to either the cannabis oil or a placebo, and 87 completed the study. The median age of participants was 63, and they had lived with a diagnosis of Parkinson’s for a median of seven years.
During the first three weeks, the researchers adjusted each patient’s dose, starting at two drops twice a day. If side effects occurred, the dose could be reduced. If the treatment was tolerated, it was gradually increased to eight drops twice daily. The final daily dose was 43.88 mg of CBD and 0.96 mg of THC. Patients then stayed on their final dose for six weeks.
The main outcome was pain measured with the Parkinson’s Disease Pain Classification System (PD-PCS). The researchers also used the Brief Pain Inventory (BPI), which measures the severity of pain and its interference with daily life, to assess how many patients had at least a 30% reduction in pain.
However, there was no significant difference in pain between patients who received the cannabis oil and those who received a placebo, regardless of whether it was measured using the PD-PCS or the BPI. There was also no significant difference in the proportion of patients who had at least a 30% reduction in pain.
Further studies with larger [patient populations] and higher concentrations of CBD and THC are warranted.
An interim analysis showed that continuing the study was unlikely to demonstrate a benefit. The study was therefore stopped early for futility, meaning the treatment was unlikely to prove effective for pain under the conditions tested. The cannabis oil also failed to outperform the placebo in easing other nonmotor symptoms.
Most side effects were mild. Irritability occurred more often in the group of patients who received the cannabis oil (17%) than in the placebo group, where none of the patients experienced this side effect. Two serious medical events occurred, Guillain–Barré syndrome and cryptococcal meningitis, but neither was deemed related to the treatment.
Although treatment with the cannabis oil for nine weeks “did not result in a significant improvement in pain,” it was relatively safe and well-tolerated, the researchers wrote. As study limitations, the team noted the small number of participants and a lack of “laboratorial monitoring” during follow-up.
“Further studies with larger [patient populations] and higher concentrations of CBD and THC are warranted,” the researchers concluded, writing that “the favorable safety profile supports future trials.”
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