THC/CBD Spray for MS Nerve Pain Showed Mixed Results but Prevented Relapse When Stopped
A phase III trial of THC/CBD spray for multiple sclerosis neuropathic pain did not meet its primary endpoint at 14 weeks, but a subsequent withdrawal phase showed that patients on the spray were significantly less likely to lose pain control when switched to placebo.
Quick Facts
What This Study Found
This study had two phases. In Phase A, 339 MS patients with neuropathic pain were randomized to THC/CBD spray or placebo for 14 weeks. The primary endpoint (30% pain reduction responder rate) was not met: 50% responded on THC/CBD versus 45% on placebo (p=0.234). However, a pre-planned interim analysis at week 10 showed a significant difference favoring THC/CBD (p=0.046).
In Phase B, 58 responders were re-randomized to continue THC/CBD spray or switch to placebo for 4 weeks. The results were clear: 57% of placebo patients lost treatment benefit versus only 24% on THC/CBD spray (p=0.04). Pain scores and sleep quality also significantly favored continued treatment.
Key Numbers
Phase A: 339 patients (167 THC/CBD, 172 placebo). 50% vs 45% responders (p=0.234). Week 10 interim: significant (p=0.046). Phase B: 58 patients. Treatment failure: 57% placebo vs 24% THC/CBD (p=0.04). Pain difference: -0.79 points (p=0.028). Sleep quality: +0.99 points (p=0.015).
How They Did This
Phase III, double-blind, placebo-controlled, two-phase study. Phase A: parallel-group, 339 patients, 14-week THC/CBD spray vs. placebo. Phase B: randomized withdrawal in 58 responders, 4 weeks. Primary Phase A endpoint: 30% responder rate at week 14. Primary Phase B endpoint: time to treatment failure.
Why This Research Matters
While the primary Phase A endpoint was not met, the Phase B withdrawal design clearly demonstrated that THC/CBD spray maintains pain control. The high placebo response rate in Phase A (45%) likely obscured a real treatment effect, a common problem in pain trials.
The Bigger Picture
This study illustrates the challenge of pain clinical trials: high placebo response rates can mask real treatment effects. The enriched enrollment, randomized withdrawal design (Phase B) may be a better approach for demonstrating cannabinoid pain efficacy. This design has since become more common in pain research.
What This Study Doesn't Tell Us
Phase A did not meet its primary endpoint, limiting regulatory conclusions. Phase B had a small sample (58 patients). The 4-week withdrawal phase was short. The high placebo response complicates interpretation. Not all Phase A participants entered Phase B, introducing selection bias.
Questions This Raises
- ?Would a larger Phase B trial confirm these findings?
- ?Is the enriched enrollment, randomized withdrawal design the right approach for cannabinoid pain trials?
- ?What characterizes the 50% of patients who respond to THC/CBD spray?
Trust & Context
- Key Stat:
- 57% lost pain control when switched to placebo vs. 24% continuing THC/CBD spray
- Evidence Grade:
- Phase III RCT with mixed results; moderate evidence with clear withdrawal-phase demonstration of efficacy.
- Study Age:
- Published in 2013. THC/CBD spray (nabiximols) has continued regulatory development for MS pain.
- Original Title:
- A double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD oromucosal spray in combination with the existing treatment regimen, in the relief of central neuropathic pain in patients with multiple sclerosis.
- Published In:
- Journal of neurology, 260(4), 984-97 (2013)
- Authors:
- Langford, R M, Mares, J, Novotna, A, Vachova, M, Novakova, I, Notcutt, W, Ratcliffe, S
- Database ID:
- RTHC-00694
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does THC/CBD spray work for MS nerve pain?
The results were mixed. In a straightforward 14-week comparison, THC/CBD spray was not significantly better than placebo (50% vs 45% response). However, when responders were re-randomized, those switched to placebo were much more likely to lose pain control (57% vs 24%), showing the spray was genuinely maintaining pain relief. The high placebo response rate may have obscured the drug's real effect.
Why did the placebo response rate make the study fail?
Pain trials often have high placebo response rates because pain is subjective and influenced by expectations, attention, and the act of receiving treatment. When 45% of placebo patients reported 30% pain improvement, the true drug effect was hard to detect statistically. The withdrawal phase addressed this by showing that removing the active drug clearly worsened outcomes.
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Cite This Study
https://rethinkthc.com/research/RTHC-00694APA
Langford, R M; Mares, J; Novotna, A; Vachova, M; Novakova, I; Notcutt, W; Ratcliffe, S. (2013). A double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD oromucosal spray in combination with the existing treatment regimen, in the relief of central neuropathic pain in patients with multiple sclerosis.. Journal of neurology, 260(4), 984-97. https://doi.org/10.1007/s00415-012-6739-4
MLA
Langford, R M, et al. "A double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD oromucosal spray in combination with the existing treatment regimen, in the relief of central neuropathic pain in patients with multiple sclerosis.." Journal of neurology, 2013. https://doi.org/10.1007/s00415-012-6739-4
RethinkTHC
RethinkTHC Research Database. "A double-blind, randomized, placebo-controlled, parallel-gro..." RTHC-00694. Retrieved from https://rethinkthc.com/research/langford-2013-a-doubleblind-randomized-placebocontrolled
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.