The Research Department
By Ted Swing, Ph.D.

When a person experiences a broken bone or other injury to one of the extremities, they typically receive medical attention and the fracture heals over time. However, for a small number of people who have such a fracture or other injury they develop a chronic pain condition called complex regional pain syndrome (CRPS). This condition has also been known as reflex sympathetic dystrophy (RSD). In even more rare cases it can occur with no precipitating injury. Symptoms of CRPS include burning or throbbing pain (typically in the injured limb), changes in the skin’s color, temperature, or texture in the area near the injury, sensitivity to touch or cold, swelling, muscle atrophy, and muscle contracture. For some these symptoms go away on their own, but for others they can last months or years.

New Study

Though patients with CRPS may experience relief from various medications and therapies, it has proven difficult to treat for some patients. The FDA has not approved a pharmacological treatment specifically for CRPS in the U.S. However, a pharmaceutical company Grünenthal has begun a clinical trial in the US for one possible CRPS treatment — a drug called neridronic acid. In a previous study of 82 patients conducted in Italy, half of these patients received an infusion of this drug four times over a 10-day period while the other half received infusions of a placebo. Those treated with neridronic acid experienced significant reductions in pain and other CRPS symptoms compared to the placebo group.

The new study, sponsored by Grünenthal, will treat patients with CRPS type I (which makes up roughly 90% of CRPS cases). These patients will be randomly assigned to receive either a high dose of neridronic acid, a low dose of neridronic acid or a placebo infusion. After meeting study enrollment criteria, a patient will come to a surgery center four times (Day 1, Day 4, Day 7 and Day 10) and provide blood and urine samples, and undergoes EKG testing to ensure safety. Once they are safe to proceed, they will receive an infusion of the assigned treatment lasting three hours. After these infusions, patients will return for up to six follow up visits over the next 12 months to assess the safety and efficacy of the treatment.

Adults with CRPS-I who are in a stable treatment for at least one month may qualify if they lack certain exclusionary conditions renal impairment or certain cardiovascular conditions. If you are interested in learning more about this study, you can speak with your pain management providers or contact me directly at

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