Single cannabis inhalation showed limited pain relief in fibromyalgia patients | Research

The takeaway

In a rigorous crossover trial of 20 fibromyalgia patients, no cannabis variety outperformed placebo on spontaneous or electrical pain, though THC-containing varieties increased pressure pain thresholds and the THC+CBD combination showed more patients with 30% pain reduction.

Fibromyalgia patients considering cannabis, pain researchers, and clinicians advising on cannabinoid therapy.

CBD reduced THC analgesic effects despite raising THC blood levels

What the researchers found

None of the four treatments (high-THC, THC+CBD, high-CBD, placebo) had greater effect than placebo on spontaneous or electrical pain. However, THC-containing varieties significantly increased pressure pain threshold. More patients receiving THC+CBD (Bediol) showed 30% pain reduction compared to placebo (90% vs 55%). CBD inhalation increased THC plasma concentrations but diminished THC-induced analgesic effects, suggesting pharmacokinetic synergy but pharmacodynamic antagonism.

Why it matters

This is one of the few rigorous RCTs testing pharmaceutical-grade cannabis in fibromyalgia, a condition where many patients self-medicate with cannabis. The complex THC-CBD interaction findings challenge simple assumptions about cannabinoid combinations.

The numbers in context

20 patients. Bedrocan: 22.4mg THC. Bediol: 13.4mg THC + 17.8mg CBD. Bedrolite: 18.4mg CBD. 90% vs 55% achieved 30% pain reduction (Bediol vs placebo, p=0.01). Pain scores correlated with drug high (ρ=-0.5, p<0.001).

How the study worked

Randomized placebo-controlled 4-way crossover trial with 20 fibromyalgia patients. Four varieties tested: Bedrocan (22.4mg THC), Bediol (13.4mg THC + 17.8mg CBD), Bedrolite (18.4mg CBD), and placebo. Single vapor inhalation with 3-hour monitoring.

What this study cannot tell us

Only 20 patients. Single inhalation rather than sustained treatment. Fibromyalgia-specific results may not apply to other pain conditions. Correlation between pain relief and feeling high raises questions about whether analgesic effects are truly separate from psychoactive effects.

How to read the evidence

Well-designed crossover RCT with pharmaceutical-grade products, but very small sample and single-dose design.

When this study was published

2019 clinical trial.

The bigger picture

The finding that CBD increased THC blood levels but reduced its pain-relieving effects complicates the popular narrative that THC and CBD work better together for all conditions.

Questions still open

Would repeated dosing over weeks produce different results? Does the THC-CBD antagonism for pain occur at different ratios? Is the pain relief primarily a psychoactive effect?

Common questions

Does cannabis help fibromyalgia pain?

In this single-dose trial, no cannabis variety clearly outperformed placebo on pain measures, though more patients receiving THC+CBD reported meaningful pain reduction than placebo (90% vs 55%).

Does adding CBD to THC improve pain relief?

Surprisingly, CBD increased THC blood levels but reduced its pain-relieving effects in this study, suggesting the interaction between these cannabinoids is more complex than commonly assumed.

Read the original research

An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia.

Pain, 160(4), 860-869

View on PubMed ↗Publisher’s paper ↗

Citation

van de Donk, Tine; Niesters, Marieke; Kowal, Mikael A; Olofsen, Erik; Dahan, Albert; van Velzen, Monique. (2019). An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia.. Pain, 160(4), 860-869. https://doi.org/10.1097/j.pain.0000000000001464