CRPS: when an injury's pain won't switch off — and where topical ketamine fits

Sometimes an injury heals, but the pain doesn't leave. In Complex Regional Pain Syndrome (CRPS), a limb that was hurt — often after surgery or trauma — keeps sending out intense, burning, out-of-proportion pain, sometimes with swelling, colour changes, or sensitivity to the lightest touch.

Why it's so hard to treat

CRPS involves several things at once — irritated nerves, inflammation, and changes in how the nervous system processes signals. Few medications are clearly effective, which pushes patients and prescribers to look for additional options.

Where ketamine comes in

Ketamine calms a specific overactive pain pathway (the NMDA receptor). Delivered as a compounded topical cream, the goal is to act near the painful area while keeping more of the drug out of the bloodstream — which may mean fewer whole-body side effects.

An honest look at the evidence

This is promising, not proven. In one published clinic review of people with CRPS using topical ketamine, about half reported improvement, while others did not — and notably, no one reported side effects. That favourable safety picture is encouraging, but researchers are clear: larger, controlled studies are needed, and topical ketamine isn't a first-line therapy. It's a reasonable option to discuss, especially when standard approaches fall short.

Read next: "What does the evidence really say about compounded pain creams?"

This article is general information, not medical advice. Compounded preparations are customized prescriptions, not Health Canada–approved drug products, and the evidence behind them varies by ingredient and condition. Whether any treatment is right for you depends on your individual health — please speak with your prescriber and pharmacist. Orleans Compounding Community Pharmacy · 2746 St-Joseph Blvd, Unit 100, Orléans, ON · 613-824-3111.