Investigation of the anti-inflammatory, antinociceptive effect of ellagic acid as measured by digital paw pressure via the Randall-Selitto meter in male Sprague-Dawley rats.

Ellagic acid (EA), a dietary supplement, is purported to have anti-inflammatory, antinociceptive properties via cyclooxygenase (COX) inhibition. We measured the antinociceptive efficacy of EA alone and in combination with a nonselective COX inhibitor and a selective COX-2 inhibitor. We assigned 54 male Sprague-Dawley rats to 1 of 6 groups to be given the following compounds: (1) vehicle, (2) ketorolac (nonselective COX inhibitor), (3) meloxicam (selective COX-2 inhibitor), (4) EA, (5) EA plus ketorolac, and (6) EA plus meloxicam. Inflammatory pain was induced in the right hind paw by injecting carrageenan. Rats were given study compounds via intraperitoneal injection 30 minutes after paw injections. Pain tolerance was assessed using the Randall-Selitto instrument at 30 minutes and 4, 8, 12, and 24 hours. The highest pressure tolerated was recorded in grams. The analysis of variance suggested a significant difference (F = 2.44; P = .048). The least significant difference post hoc analysis suggested that at 8 hours, EA plus ketorolac provided greater antinociception than all other compounds (P = .04). Furthermore the combination of EA plus ketorolac provided longer antinociception than all other compounds (P = .03) such that EA plus ketorolac was effective at 24 hours.