Capsaicin May Reduce Acute Postsurgical Pain

SAN FRANCISCO — Instilling purified capsaicin into a surgical wound after open mesh groin hernia repair and before wound closure reduced postoperative pain scores, compared with placebo, for 3 days after surgery, according to a randomized, double-blind, placebo-controlled study of 41 men.

There was no significant difference between groups, however, in the primary end point: average daily pain scores during the first week after surgery, Dr. Eske K. Aasvang reported in a poster presentation at the annual meeting of the American Society of Anesthesiologists.

Average pain scores, as assessed on a 100-point visual analog scale, were less than 15 after postoperative day 4 in both groups—too low to show a treatment difference in the second half of the week, suggested Dr. Aasvang of the University of Copenhagen and his associates.

Dr. Aasvang received a salary from the maker of the capsaicin formulation, Anesiva Inc., which also funded the study.

Patients received a single intraoperative instillation of 15 mL of medication containing either placebo or 1,000 mcg of Adlea, a formulation consisting of more than 98% capsaicin. All patients also were given acetaminophen and ibuprofen for postoperative analgesia and were allowed to take tramadol if needed.

The morning after surgery, median pain scores on the visual analog scale were approximately 13 in the capsaicin group and 33 in the placebo group. Median pain scores in the capsaicin group and the placebo group on the second morning after surgery were approximately 15 and 25, respectively, and on the third morning were approximately 7 and 17, respectively.

Four patients in the capsaicin group and none in the placebo group developed treatment-related adverse events, including increased blood pressure (two patients), decreased heart rate (one), and abnormal skin odor (one). Dr. Aasvang described the capsaicin formulation as “generally well tolerated” in this study.

All patients except one in the placebo group had normal wound healing in the week after surgery. One patient in the placebo group had surgical wound drainage, a serious adverse event that was thought to be unrelated to the study treatment.

The study results suggest that purified capsaicin may have a role to play in reducing acute postoperative pain, the investigators concluded.