A randomized study of the effects of single-dose gabapentin versus placebo on postoperative pain and morphine consumption after mastectomy.

BACKGROUND: The anticonvulsant gabapentin has proven effective for neuropathic pain in three large placebo-controlled clinical trials. Experimental and clinical studies have demonstrated antihyperalgesic effects in models involving central neuronal sensitization. It has been suggested that central neuronal sensitization may play an important role in postoperative pain. The aim of the study was to investigate the effect of gabapentin on morphine consumption and postoperative pain in patients undergoing radical mastectomy.

METHODS: In a randomized, double-blind, placebo-controlled study, 70 patients received a single dose of oral gabapentin (1,200 mg) or placebo 1 h before surgery. Patients received patient-controlled analgesia with morphine at doses of 2.5 mg with a lock-out time of 10 min for 4 h postoperatively. Pain was assessed on a visual analog scale at rest and during movement, and side effects were assessed on a four-point verbal scale 2 and 4 h postoperatively.

RESULTS: Thirty-one patients in the gabapentin group and 34 patients in the placebo group completed the study. Gabapentin reduced total morphine consumption from a median of 29 (interquartile range, 21-33) to 15 (10-19) mg (P< 0.0001). Pain during movement was reduced from 41 (31-59) to 22 (10-38) mm at 2 h postoperatively (P < 0.0001) and from 31 (12-40) to 9 (3-34) mm at 4 h postoperatively (P = 0.018). No significant differences between groups were observed with regard to pain at rest or side effects.

CONCLUSION: A single dose of 1,200 mg oral gabapentin resulted in a substantial reduction in postoperative morphine consumption and movement-related pain after radical mastectomy, without significant side effects. These promising results should be validated in other acute pain models involving central neuronal sensitization.