BACKGROUND: Preemptive analgesia is an antinociceptive treatment that prevents the development of central sensitization which contributes to the post-injury pain hypersensitivity. But controversies exist over the effectiveness and clinical value of preemptive analgesia. The aim of this study is to evaluate the preemptive effect of intrathecal bupivacaine on incisional pain in rats. METHODS: Thirty male rats were divided into 3 groups, saline-treated control group (n=10), post-treatment group (n=10), and pre-treatment group (n=10) according to the time which intrathecal administration of bupivacaine was done. To evaluate postoperative mechanical hyperalgesia in injured feet, withdrawal frequency and withdrawal thresholds were measured by von Frey filaments at 30 min, 1 hr, 2 hrs, 3 hrs, 1 day, 3 days and 7 days after incision. RESULTS: In control group, the withdrawal frequency increased from 0+/-0% before incision to 98.0+/-1.3% after the foot incision and the responses gradually declined during the postoperative 7 days to 52.0+/-4.7%. The median withdrawal threshold decreased from 148.43 mN before incision to 0.05 mN after foot incision and gradually increased during the postoperative 7 days to 6.79 mN. The post-treatment group showed no significant differences in the withdrawal frequency and withdrawal thresholds when compared with control group at post-operative 1 hour and thereafter (P<0.05). The pre-treatment group showed significantly lower withdrawal frequency and significantly higher withdrawal threshold compared with control group at postoperative 30 min and thereafter (P<0.05), and significantly lower withdrawal frequency and higher withdrawal threshold compared with post-treatment group at postoperative 2 hours and thereafter (P<0.05). CONCLUSION: We conclude that intrathecal bupivacaine administered before incision reduces postoperative delayed hyperalgesia in incisional pain model, and it may result from preventing the development of injury- induced central sensitization.