Morphine exacerbates CCI allodynia when dosing begins 10 days after injury. Chronic constriction injury surgeries were performed with one 6–0 chromic gut suture. Morphine (5 mg/kg twice per day) or equivolume saline was administered for 5 days, beginning at day 10 after surgery. (A) Von Frey testing was conducted before and after CCI surgery, and after completion of opioid administration. (B) Area-under-the-curve analysis of von Frey threshold of all timepoints after morphine treatment. BL: baseline, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. n = 6/group. CCI, chronic constriction injury.