Evidence by molecule
How strong the research is for each treatment, on our four-level evidence scale. Each links to the full molecule guide.
A review of 7 randomised trials (211 people) found a small pain reduction lasting up to two weeks after an infusion. Trials are small and differ widely in design.
What the research shows
Ketamine is the only substance on this site with meaningful research for chronic pain. It’s long used in anaesthesia and acute pain. A 2019 meta-analysis of seven randomised trials (211 people) found that ketamine infusions gave a small reduction in chronic pain, about 1.8 points on a 10-point scale, lasting up to two weeks after the infusion. In the three trials that reported it, more people responded to ketamine than to placebo (51% vs 19%).1 See our ketamine guide.
Classic psychedelics such as psilocybin are only beginning to be studied for chronic pain, and there aren’t yet enough published trials to rate.
Established treatments
Chronic pain is usually managed with a combination of approaches, such as physical therapy, psychological therapies and medicines. Talk to a qualified health professional about your own situation.
Studies in the library
- Repeated ketamine infusions for arthritis pain: a 38-patient chart reviewObservational · 2026 · Evidence: Low
- Review of classic psychedelics for chronic pain: early signals, weak evidence so farOther · 2026 · Evidence: Low
- Review of 18 trials finds oral ketamine mostly causes mild, short-lived side effectsSystematic review · 2026 · Evidence: Low
- Review: how salvinorin A acts on opioid receptors rather than serotonin receptorsOther · 2026 · Evidence: Very low
- Psilocybin versus active placebo for migraine prevention: small trial finds no clear differenceRCT · 2025 · Evidence: Very low
- Ketamine drip for acute injury pain linked to lower PTSD and anxiety scores at 6 monthsRCT · 2025 · Evidence: Moderate
- Cognitive scores after 5-day ketamine infusions for hard-to-treat chronic migraineObservational · 2025 · Evidence: Low
- Comparing 3-, 5- and 7-day ketamine infusion schedules for complex regional pain syndromeRCT · 2025 · Evidence: Moderate
References
- Orhurhu V, et al. Ketamine infusions for chronic pain: a systematic review and meta-analysis of randomized controlled trials. Anesthesia & Analgesia. 2019;129(1):241–254. Source