Oral tablets containing purified tetrahydrocannabinol, or THC, failed to improve chronic abdominal pain better than placebo in a phase 2 randomized controlled trial.
Researchers noted that oral THC “showed acceptable safety and tolerability profiles” as an add-on treatment, and that “further research should evaluate the effects of THC on secondary and tertiary central pain processing.”
“The introduction of cannabis for the treatment of chronic abdominal pain offers an interesting alterative,” Marjan de Vries, MD, of the department of surgery at Radboud University Medical Center in the Netherlands, said in an AGA video abstract. “Delta-9-tetrahydrocannabinol, or THC, is the main psychoactive component of the cannabis plant, which has been used for already many centuries. However, the therapeutic potential of THC is still not clear.”
To evaluate the analgesic effects of a novel oral THC tablet (Namisol; Echo Pharmaceuticals), as well as its pharmacokinetics, safety and tolerability in patients with chronic abdominal pain, de Vries and colleagues randomly assigned 65 patients with at least 3 months of chronic abdominal pain due to surgery or chronic pancreatitis to receive the tablets or placebo for 50 days. All patients received instructions to continue taking their prescribed medications, including analgesics, throughout the study period.
Patients first took the THC tablets in a step-up phase, beginning at 3 mg three times per day for 5 days, and then 5 mg three times per day for 5 days, and then switched to a stable dose of 8 mg three times per day. Pain relief measured by visual analogue scale served as the primary endpoint.
At the end of the study period, mean pain scores were statistically comparable between THC and placebo groups, and decreased by 40% in the THC group and 37% in the placebo group.
Secondary endpoints, including patient-reported pain and quality of life, pharmacokinetics and safety, were also comparable. Further, plasma samples showed oral THC was “generally well-absorbed.”
Finally, seven patients stopped taking THC tablets due to adverse events compared with two patients who received placebo, all of which were mild or moderate.
“We concluded that THC was not effective for the treatment of chronic abdominal pain,” de Vries said in the video abstract. “We observed a large placebo effect, which might be due to the high expectations associated with this drug,” she added.
“We were surprised by the results of this study,” Harry van Goor, MD, PhD, also of the department of surgery at Radboud University Medical Center, concluded in the video abstract. “We will not follow up this phase 2 study with a phase 3 study because we do not believe in a larger population this drug will show efficacy in a difficult-to-treat patient group with chronic abdominal pain.” – by Adam Leitenberger
Disclosures: The researchers report no relevant financial disclosures.