Objective To investigate the effects of the single and the continuous pentoxifylline (PTX) injection of prior intraperitoneal administration applied on the plantar incision-induced postoperative hyperalgesia in rats. Methods The postoperative pain rats model with plantar incision were used for this experiment.All sixty adult male Sprague-Dawley rats weighting 180 g-250 g were randomly divided into two groups:single-dose group (group Ⅰ ) and the continuous treatment group (group Ⅱ ).The group Ⅰ was divided into 5 subgroups (n=6):control group (group C) was given normal saline (NS),PTX treatment groups (group PTX1-4) were given 12.5,25,50,100 mg/kg PTX by single time intraperitoneal administration.Group Ⅱ was divided into 5 subgroups (n=6):control group (group C) was given NS,pentoxifylline treatment groups (group PTX1-4) were administered PTX (12.5,25,50,100 mg/kg intraperitoneally) systemically daily.In the preoperative 30 min,all subgroups of the group Ⅰ were given different doses of PTX intraperitoneally and the corresponding volume of NS,and measured at each time point of the mechanical withdrawal threshold (MWT),thermal withdrawal latency and withdrawal duration at pre-incision (T0),then 1,3,5 h after surgery (T1-3).From 30 min before the operation to day1-7 post-operation,all subgroups of the group Ⅱ were systemically daily intraperitoneally administrated different doses of PTX and the corresponding volume of NS,and measured at each time point of the mechanical withdrawal threshold (MWT),thermal withdrawal latency and withdrawal duration at pre-incision (T0),then 1,2,3,5,7 d after surgery (T1-6).Results ① Comparison in the groups:in group Ⅰ,MWT was higher at T1 than at T2 in group PTX3,4 (P＜0.05 or P＜0.01 ).Compared with them in group PTX3,4 at T3,MWT was increased at T1-2,and thermal withdrawal latency threshold was increased too,following thermal withdrawal duration reduced at T1(P＜0.05 or P＜0.01 ).② Comparison between groups:in group Ⅰ,compared with group C,MWT was significantly raised at T1-2 in group PTX3,4.Furthermore,thermal threshold latency threshold was up-regulated and thermal withdrawal duration was down-regulated at T1 in group PTX3 and at T1-2 in group PTX4 (P＜0.05 or P＜0.01 ).In group Ⅱ,compared with group C,MWT was significantly increased at T1-4 in group PTX3,4.Thermal threshold latency threshold was up-regulated at T1 in group PTX3 and at T1-4 in group PTX4.Thermal withdrawal duration was negative regulator at T1-2 in group PTX3 and at T1-3 in group PTX4 in addition (P＜0.05 or P＜0.01 ).There data shown none significant difference among group PTX1,2 with group C,in group Ⅰ and Ⅱ (P＞0.05). Conclusions Pentoxifylline can effectively reduce the plantar incisioninduced mechanical allodynia and heat hyperalgesia expression lever in rats,meanwhile showed a dose-dependent analgesic effect.