Abstract
The present study aimed to evaluate the anti-inflammatory effects of pentoxifylline (PTX), a non-specific phosphodiesterase inhibitor in the rat. Acute inflammation was induced by subplantar injection of carrageenan (1%) in the rat hind paw. Results showed that intraperitoneal (i.p.) administration of PTX (36 or 72
mg
kg
−1) 30
min prior to carrageenan reduced the paw oedema response in dose-dependent manner with a maximal effect of 18.9 and 40.1%, respectively, at 2
h post-carrageenan (
P<0.001 and <0.001 at respective doses). Theophylline given at equimolar doses (29.9 or 45.8
mg
kg
−1, i.p.) did not reduce the oedema response. With higher doses of PTX (144–300
mg
kg
−1, i.p.) the anti-oedema effect of the drug was more pronounced, but mainly confined to the first 2
h following carrageenan injection and decreasing rapidly thereafter. PTX (72
mg
kg
−1, i.p.) given 30
min after carrageenan challenge reduced the oedema response by 24.7 and 26.2% at 1 and 2
h after dosing (
P<0.05 and <0.05, respectively). PTX (36 or 72
mg
kg
−1, i.p.) co-administered with indomethacin (5
mg
kg
−1, i.p.) 30
min before carrageenan had little modulatory effect on the anti-oedema effect of indomethacin, but the higher dose of PTX (144
mg
kg
−1, i.p.) reduced the anti-inflammatory effect of indomethacin by 24% at 4
h post-carrageenan. PTX (72
mg
kg
−1, i.p.) enhanced the anti-oedema effect of the selective COX-2 inhibitor celecoxib (33
mg
kg
−1, i.p.) by 55.1% at 4
h post-carrageenan. In contrast, the higher dose of PTX (144
mg
kg
−1, i.p.) reduced the anti-oedema effect of celecoxib by 46.8% at 4
h post-carrageenan. PTX (36 or 72
mg
kg
−1) enhanced the anti-oedema effect of dexamethasone (0.1
mg
kg
−1) with maximal effect of 76 and 104.8% at 2
h post-carrageenan (
P<0.01 and <0.01 for respective doses). PTX (0.6
mg per paw) given with carrageenan into the rat hind paw reduced the oedema response with a maximal effect of 33.4% at 1
h following carrageenan. PTX (0.6
mg per paw) given in the contralateral hind paw reduced the carrageenan-induced paw oedema for 1
h by 32.2%. Thus, PTX, when given at doses comparable to those used in man for treatment of circulatory disorders displayed anti-inflammatory in vivo and enhanced the anti-inflammatory effect of a selective COX-2 inhibitor or dexamethasone. PTX may have therapeutic potential as anti-inflammatory agent either alone or in combination with non-steroidal anti-inflammatory drugs or with steroids. There is also an intriguing possibility for the use of topical preparations for the management of local inflammatory conditions.