Complex Regional Pain Syndrome: Bisphosphonate, Ketamine, or Gabapentinoid First
A woman recently diagnosed with complex regional pain syndrome needs to start treatment while the condition is still in its most treatable early phase, and the three real evidence-backed options work through completely different mechanisms with no trial ever comparing them directly.
C.V., a 29-year-old woman, fractured her left wrist eleven weeks ago in a bicycle accident, a straightforward fracture that healed on imaging within the expected timeline — but the pain never followed the same course. What should have resolved as the cast came off instead intensified: her hand is now warm, visibly swollen compared to the right, and touching it, even lightly, produces pain out of proportion to any stimulus that should cause it. A hand surgeon referred her to a pain specialist six weeks ago, and a triple-phase bone scan ordered at that visit showed increased periarticular uptake consistent with the bone-turnover changes seen in early complex regional pain syndrome. She works as a graphic designer, a job now genuinely threatened by a hand she can barely bring into contact with a keyboard, and both she and her pain specialist are aware that CRPS treated early, within the first several months, carries meaningfully better odds of real improvement than the same condition addressed after it becomes chronic.
Three pharmacologic options carry real supporting evidence for CRPS, and they work through genuinely different mechanisms with no trial ever comparing them head-to-head. Varenna and colleagues' randomized, placebo-controlled trial of intravenous neridronate — a bisphosphonate — found a substantial, statistically significant reduction in pain in CRPS patients, a population the trial characterized as having exactly the early, warm-phase presentation and bone-turnover findings her own bone scan shows. Separately, Sigtermans and colleagues' randomized trial of intravenous ketamine in CRPS found a real, significant reduction in pain scores — an honest reading of that same trial also has to note it found no corresponding improvement in functional measures, a limitation worth stating alongside the positive pain finding rather than only citing the part that sounds better. Gabapentinoids, by contrast, carry a smaller and less CRPS-specific evidence base, but a far simpler, lower-risk, more accessible path — no infusion center, no specialized monitoring, a prescription she could start this week.
Multidisciplinary CRPS planning visit
Her bone scan shows exactly the pattern Varenna's neridronate trial enrolled for — early, warm-phase CRPS with periarticular bone-turnover changes — and that trial found a substantial, statistically significant pain reduction. When a patient's own presentation matches a positive trial's population this closely, I think that match should carry real weight in the decision.
The population match is real, and I'm not disputing it. But her exam is also showing prominent allodynia and hyperalgesia — features that point toward central sensitization as much as bone involvement, which is exactly what ketamine's NMDA-antagonist mechanism targets. Sigtermans' trial found a real, significant reduction in pain scores with IV ketamine in CRPS.
I want to be honest about that same trial rather than cite only its favorable half: it found no corresponding improvement in functional measures. I'm citing it for the pain reduction it did show, not overstating what it showed about function.
Both trials are real and both of you are reading them honestly. But neither of you has argued against starting with a gabapentinoid first — it's lower-risk, doesn't require a 90-minute drive to an infusion center, and gives a real, if more modest, shot at her neuropathic pain component while the more specialized options stay in reserve rather than being front-loaded before a simpler one's been tried. Given how time-sensitive early CRPS treatment is, starting something accessible today shouldn't lose out to a debate over which infusion therapy is theoretically stronger.
Neither the neridronate nor the ketamine case is wrong on the evidence — the argument for sequencing is about not letting logistics delay treatment while that argument gets settled.
Agreed: gabapentin started immediately for accessibility and time-sensitivity, a neridronate infusion course scheduled at the regional center given her direct match to the trial population, and ketamine named explicitly as the next step if central-sensitization features persist once the first two are underway. All three voices signed onto starting more than one therapy in sequence rather than picking a single winner, once the pharmacologist reframed the question as sequencing rather than mechanism ranking.
Not agreed: whether neridronate and gabapentin should have been started simultaneously, as planned, or neridronate held until gabapentin's own effect could be assessed in isolation. The rheumatologist's concern is that CRPS's early treatment window is narrow enough that sequential, one-at-a-time trials risk losing that window before the more evidence-matched therapy ever starts; the pharmacologist's view is that starting both introduces a confound if either works. Both therapies proceeded in parallel, with the confound risk explicitly logged rather than resolved.