A pilot trial of intravenous pamidronate for chronic low back pain.

Intravenous (i.v.) bisphosphonates relieve pain in conditions such as Paget's disease of bone, metastatic bone disease, and multiple myeloma. Based on positive findings from a prior case series, we conducted a randomized placebo-controlled study to assess the analgesic effect of i.v. pamidronate in subjects with chronic low back pain (CLBP) and evidence of degenerative disease of the spine. Four groups of 11 subjects (7 active, 4 placebo) were enrolled at escalating dose levels of 30, 60, 90, and 180 mg pamidronate (the latter administered as two 90 mg infusions). Primary outcomes were safety and change from baseline in average daily pain scores, recorded at 1, 2, 3, and 6 months postinfusion using electronic diaries. Secondary outcomes included responder rate, daily worst pain, and pain-related interference with daily function. There were no pamidronate-related serious adverse events or other significant safety findings. A statistically significant overall treatment difference in pain scores was observed, with clinically meaningful effects persisting for 6 months in the 180 mg pamidronate group. Least squares mean changes in daily average pain score were -1.39 (SE=0.43) for placebo, and -1.53 (0.71), -1.26 (0.81), -1.42 (0.65), and -4.13 (0.65) for pamidronate 30, 60, 90, and 180 mg, respectively (P=0.012 for pamidronate 180 mg vs placebo). The proportion of responders, changes in worst pain, and pain interference with daily function were also significantly improved for pamidronate 180 mg compared with placebo. In conclusion, i.v. pamidronate, administered as two 90 mg infusions, decreased pain intensity for 6 months in subjects with CLBP.